rtpengine/lib/codeclib.c

#include "codeclib.h"
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libavfilter/avfilter.h>
#include <libavutil/opt.h>
#include <glib.h>
#include <dlfcn.h>
#include "str.h"
#include "loglib.h"
#include "resample.h"
#include "rtplib.h"
#include "dtmflib.h"
#include "fix_frame_channel_layout.compat"
#include "codecmod.h"
#include "cchain.h"



#define PACKET_SEQ_DUPE_THRES 100
#define PACKET_TS_RESET_THRES 5000 // milliseconds



#define cdbg(x...) ilogs(internals, LOG_DEBUG, x)



static int generic_silence_dtx(decoder_t *, GQueue *, int);

static int generic_cn_dtx_init(decoder_t *);
static void generic_cn_dtx_cleanup(decoder_t *);
static int generic_cn_dtx(decoder_t *, GQueue *, int);



const codec_type_t codec_type_avcodec = {
	.def_init = avc_def_init,
	.decoder_init = avc_decoder_init,
	.decoder_input = avc_decoder_input,
	.decoder_close = avc_decoder_close,
	.encoder_init = avc_encoder_init,
	.encoder_input = avc_encoder_input,
	.encoder_close = avc_encoder_close,
};

const dtx_method_t dtx_method_silence = {
	.method_id = DTX_SILENCE,
	.do_dtx = generic_silence_dtx,
};
const dtx_method_t dtx_method_cn = {
	.method_id = DTX_CN,
	.do_dtx = generic_cn_dtx,
	.init = generic_cn_dtx_init,
	.cleanup = generic_cn_dtx_cleanup,
};

static struct codec_def_s *__codec_defs;
static unsigned int __num_codec_defs;

static GQueue __supplemental_codecs = G_QUEUE_INIT;
const GQueue * const codec_supplemental_codecs = &__supplemental_codecs;
static codec_def_t *codec_def_cn;
static codec_def_t *codec_def_pcm16;

void (*codeclib_thread_init)(void);
void (*codeclib_thread_cleanup)(void);
void (*codeclib_thread_loop)(void);


TYPED_GHASHTABLE(codecs_by_name, str, struct codec_def_s, str_case_hash, str_case_equal, NULL, NULL)
TYPED_GHASHTABLE(codecs_by_id_alloc, void, struct codec_def_s, g_direct_hash, g_direct_equal, NULL, g_free)

static codecs_by_name codecs_by_name_ht;

static rwlock_t generic_ffmpeg_codecs_lock = RWLOCK_STATIC_INIT;
static codecs_by_id_alloc generic_ffmpeg_codecs;



codec_def_t *codec_find(const str *name, enum media_type type) {
	codec_def_t *ret = t_hash_table_lookup(codecs_by_name_ht, name);
	if (!ret)
		return NULL;
	if (type && type != ret->media_type)
		return NULL;
	return ret;
}

codec_def_t *codec_get_pcm16(void) {
	return codec_def_pcm16;
}




const char *avc_decoder_init(decoder_t *dec, const str *extra_opts) {
	const AVCodec *codec = dec->def->decoder;
	if (!codec)
		return "codec not supported";

	dec->avc.avpkt = av_packet_alloc();

	dec->avc.avcctx = avcodec_alloc_context3(codec);
	if (!dec->avc.avcctx)
		return "failed to alloc codec context";
	SET_CHANNELS(dec->avc.avcctx, dec->in_format.channels);
	DEF_CH_LAYOUT(&dec->avc.avcctx->CH_LAYOUT, dec->in_format.channels);
	dec->avc.avcctx->sample_rate = dec->in_format.clockrate;

	if (dec->def->set_dec_options)
		dec->def->set_dec_options(dec, extra_opts);

	int i = avcodec_open2(dec->avc.avcctx, codec, NULL);
	if (i) {
		ilog(LOG_ERR | LOG_FLAG_LIMIT, "Error returned from libav: %s", av_error(i));
		return "failed to open codec context";
	}

#if LIBAVCODEC_VERSION_INT >= AV_VERSION_INT(61, 19, 0)
	avcodec_get_supported_config(dec->avc.avcctx, codec, AV_CODEC_CONFIG_SAMPLE_FORMAT, 0, (const void **) &dec->avc.sample_fmts, NULL);
#else
	dec->avc.sample_fmts = codec->sample_fmts;
#endif

	for (const enum AVSampleFormat *sfmt = dec->avc.sample_fmts; sfmt && *sfmt != -1; sfmt++)
		cdbg("supported sample format for input codec %s: %s",
				codec->name, av_get_sample_fmt_name(*sfmt));

	return NULL;
}



decoder_t *decoder_new_fmt(codec_def_t *def, int clockrate, int channels, int ptime,
		const format_t *resample_fmt)
{
	return decoder_new_fmtp(def, clockrate, channels, ptime, resample_fmt, NULL, NULL, NULL);
}

bool codec_parse_fmtp(codec_def_t *def, struct rtp_codec_format *fmtp, const str *fmtp_string,
		union codec_format_options *copy)
{
	struct rtp_codec_format fmtp_store;

	if (copy)
		ZERO(*copy);

	if (!def)
		return false;
	if (!def->format_parse)
		return true;
	if (!fmtp_string)
		return true;
	if (!fmtp) {
		ZERO(fmtp_store);
		fmtp = &fmtp_store;
	}
	if (fmtp->fmtp_parsed) {
		if (copy)
			*copy = fmtp->parsed;
		return true;
	}
	bool ret = def->format_parse(fmtp, fmtp_string);
	if (ret) {
		fmtp->fmtp_parsed = true;
		if (copy)
			*copy = fmtp->parsed;
	}
	return ret;
}

decoder_t *decoder_new_fmtp(codec_def_t *def, int clockrate, int channels, int ptime,
		const format_t *resample_fmt,
		struct rtp_codec_format *fmtp, const str *fmtp_string,
		const str *extra_opts)
{
	const char *err;
	decoder_t *ret = NULL;

	err = "codec not supported";
	if (!def->codec_type)
		goto err;

	ret = g_new0(__typeof(*ret), 1);

	ret->def = def;
	ret->clockrate_fact = def->default_clockrate_fact;
	format_init(&ret->in_format);
	ret->in_format.channels = channels;
	ret->in_format.clockrate = clockrate;

	// output defaults to same as input
	ret->dest_format = ret->in_format;
	if (resample_fmt)
		ret->dest_format = *resample_fmt;

	err = "failed to parse \"fmtp\"";
	if (!codec_parse_fmtp(def, fmtp, fmtp_string, &ret->format_options))
		goto err;

	if (def->select_decoder_format)
		def->select_decoder_format(ret, fmtp);

	ret->in_format.clockrate = fraction_mult(ret->in_format.clockrate, &ret->clockrate_fact);
	ret->dec_out_format = ret->in_format;

	if (ptime > 0)
		ret->ptime = ptime;
	else
		ret->ptime = def->default_ptime;

	// init with first supported DTX method
	enum dtx_method dm = -1;
	for (int i = 0; i < NUM_DTX_METHODS; i++) {
		if (def->dtx_methods[i]) {
			dm = i;
			break;
		}
	}

	err = def->codec_type->decoder_init(ret, extra_opts);
	if (err)
		goto err;

	ret->pts = (uint64_t) -1LL;
	ret->rtp_ts = (unsigned long) -1L;

	decoder_switch_dtx(ret, dm);

	return ret;

err:
	if (ret)
		decoder_close(ret);
	if (err)
		ilog(LOG_ERR | LOG_FLAG_LIMIT, "Error creating media decoder for codec %s: %s", def->rtpname, err);
	return NULL;
}


int decoder_switch_dtx(decoder_t *dec, enum dtx_method dm) {
	if (dec->dtx.cleanup)
		dec->dtx.cleanup(dec);
	ZERO(dec->dtx);
	unsigned int i = dm;
	if (i >= NUM_DTX_METHODS)
		return -1;
	const dtx_method_t *dmp = dec->def->dtx_methods[i];
	if (!dmp)
		return -1;
	dec->dtx = *dmp;
	if (dmp->init) {
		if (dmp->init(dec)) {
			ilog(LOG_ERR, "Failed to initialise DTX (%u)", i);
			decoder_switch_dtx(dec, -1);
			return -1;
		}
	}
	return 0;
}

int decoder_set_cn_dtx(decoder_t *dec, const str *cn_pl) {
	if (decoder_switch_dtx(dec, DTX_CN))
		return -1;
	dec->dtx.cn.cn_payload = cn_pl;
	return 0;
}


gboolean decoder_has_dtx(decoder_t *dec) {
	return dec->dtx.do_dtx == NULL ? FALSE : TRUE;
}


void avc_decoder_close(decoder_t *dec) {
#if LIBAVCODEC_VERSION_INT >= AV_VERSION_INT(56, 1, 0)
	avcodec_free_context(&dec->avc.avcctx);
#else
	avcodec_close(dec->avc.avcctx);
	av_free(dec->avc.avcctx);
#endif
	av_packet_free(&dec->avc.avpkt);
}


void decoder_close(decoder_t *dec) {
	if (!dec)
		return;
	/// XXX drain inputs and outputs

	if (dec->def && dec->def->codec_type && dec->def->codec_type->decoder_close)
		dec->def->codec_type->decoder_close(dec);

	decoder_switch_dtx(dec, -1);

	resample_shutdown(&dec->resampler);
	g_free(dec);
}


int avc_decoder_input(decoder_t *dec, const str *data, GQueue *out) {
	if (!dec->avc.avpkt)
		return -1; // decoder shut down

	const char *err;
	int av_ret = 0;

	dec->avc.avpkt->data = (unsigned char *) data->s;
	dec->avc.avpkt->size = data->len;
	dec->avc.avpkt->pts = dec->pts;

	AVFrame *frame = NULL;

	// loop until all input is consumed and all available output has been processed
	int keep_going;
	do {
		keep_going = 0;
		int got_frame = 0;
		err = "failed to alloc av frame";
		frame = av_frame_alloc();
		if (!frame)
			goto err;

#if LIBAVCODEC_VERSION_INT >= AV_VERSION_INT(57, 36, 0)
		if (dec->avc.avpkt->size) {
			av_ret = avcodec_send_packet(dec->avc.avcctx, dec->avc.avpkt);
			cdbg("send packet ret %i", av_ret);
			err = "failed to send packet to avcodec";
			if (av_ret == 0) {
				// consumed the packet
				dec->avc.avpkt->size = 0;
				keep_going = 1;
			}
			else {
				if (av_ret == AVERROR(EAGAIN))
					; // try again after reading output
				else
					goto err;
			}
		}

		av_ret = avcodec_receive_frame(dec->avc.avcctx, frame);
		cdbg("receive frame ret %i", av_ret);
		err = "failed to receive frame from avcodec";
		if (av_ret == 0) {
			// got a frame
			keep_going = 1;
			got_frame = 1;
		}
		else {
			if (av_ret == AVERROR(EAGAIN))
				; // maybe needs more input now
			else
				goto err;
		}
#else
		// only do this if we have any input left
		if (dec->avc.avpkt->size == 0)
			break;

		av_ret = avcodec_decode_audio4(dec->avc.avcctx, frame, &got_frame, dec->avc.avpkt);
		cdbg("decode frame ret %i, got frame %i", av_ret, got_frame);
		err = "failed to decode audio packet";
		if (av_ret < 0)
			goto err;
		if (av_ret > 0) {
			// consumed some input
			err = "invalid return value";
			if (av_ret > dec->avc.avpkt->size)
				goto err;
			dec->avc.avpkt->size -= av_ret;
			dec->avc.avpkt->data += av_ret;
			keep_going = 1;
		}
		if (got_frame)
			keep_going = 1;
#endif

		if (got_frame) {
			cdbg("raw frame from decoder pts %llu samples %u",
					(unsigned long long) frame->pts, frame->nb_samples);

#if LIBAVCODEC_VERSION_INT < AV_VERSION_INT(57, 36, 0)
			frame->pts = frame->pkt_pts;
#endif
			if (G_UNLIKELY(frame->pts == AV_NOPTS_VALUE))
				frame->pts = dec->avc.avpkt->pts;
			dec->avc.avpkt->pts += frame->nb_samples;

			g_queue_push_tail(out, frame);
			frame = NULL;
		}
	} while (keep_going);

	av_frame_free(&frame);
	return 0;

err:
	ilog(LOG_ERR | LOG_FLAG_LIMIT, "Error decoding media packet: %s", err);
	if (av_ret)
		ilog(LOG_ERR | LOG_FLAG_LIMIT, "Error returned from libav: %s", av_error(av_ret));
	av_frame_free(&frame);
	return -1;
}

static int __decoder_input_data(decoder_t *dec, const str *data, unsigned long ts, int *ptime,
		int (*callback)(decoder_t *, AVFrame *, void *u1, void *u2), void *u1, void *u2)
{
	GQueue frames = G_QUEUE_INIT;

	if (G_UNLIKELY(!dec))
		return -1;

	if (!data && (!dec->dtx.do_dtx || !ptime))
		return 0;

	ts = fraction_mult(ts, &dec->clockrate_fact);

	cdbg("%p dec pts %llu rtp_ts %llu incoming ts %lu", dec, (unsigned long long) dec->pts,
			(unsigned long long) dec->rtp_ts, (unsigned long) ts);

	if (G_UNLIKELY(dec->rtp_ts == (unsigned long) -1L)) {
		// initialize pts
		dec->pts = 0;
	}
	else {
		// shift pts according to rtp ts shift
		uint64_t shift_ts = ts - dec->rtp_ts;
		if ((shift_ts * 1000) / dec->in_format.clockrate > PACKET_TS_RESET_THRES) {
			ilog(LOG_DEBUG, "Timestamp discontinuity detected, resetting timestamp from "
					"%lu to %lu",
					dec->rtp_ts, ts);
			// XXX handle lost packets here if timestamps don't line up?
		}
		else
			dec->pts += shift_ts;
	}
	dec->rtp_ts = ts;

	if (data)
		dec->def->codec_type->decoder_input(dec, data, &frames);
	else
		dec->dtx.do_dtx(dec, &frames, *ptime);

	AVFrame *frame;
	int ret = 0;
	unsigned long samples = 0;
	while ((frame = g_queue_pop_head(&frames))) {
		samples += frame->nb_samples;
		dec->dec_out_format.format = frame->format;
		AVFrame *rsmp_frame = resample_frame(&dec->resampler, frame, &dec->dest_format);
		if (!rsmp_frame) {
			ilog(LOG_ERR | LOG_FLAG_LIMIT, "Resampling failed");
			ret = -1;
		}
		else {
			if (callback(dec, rsmp_frame, u1, u2))
				ret = -1;
		}
		if (rsmp_frame != frame)
			av_frame_free(&frame);
	}

	if (ptime)
		*ptime = samples * 1000L / dec->in_format.clockrate;

	return ret;
}
int decoder_input_data(decoder_t *dec, const str *data, unsigned long ts,
		int (*callback)(decoder_t *, AVFrame *, void *u1, void *u2), void *u1, void *u2)
{
	if (!data || !data->s || !data->len)
		return 0;
	return __decoder_input_data(dec, data, ts, NULL, callback, u1, u2);
}
int decoder_input_data_ptime(decoder_t *dec, const str *data, unsigned long ts, int *ptime,
		int (*callback)(decoder_t *, AVFrame *, void *u1, void *u2), void *u1, void *u2)
{
	if (!data || !data->s || !data->len)
		return 0;
	return __decoder_input_data(dec, data, ts, ptime, callback, u1, u2);
}
int decoder_dtx(decoder_t *dec, unsigned long ts, int ptime,
		int (*callback)(decoder_t *, AVFrame *, void *u1, void *u2), void *u1, void *u2)
{
	return __decoder_input_data(dec, NULL, ts, &ptime, callback, u1, u2);
}


static void avlog_ilog(void *ptr, int loglevel, const char *fmt, va_list ap) {
	char *msg;
	if (vasprintf(&msg, fmt, ap) <= 0)
		ilogs(ffmpeg, LOG_ERR | LOG_FLAG_LIMIT, "av_log message dropped");
	else {
#ifdef AV_LOG_PANIC
		// translate AV_LOG_ constants to LOG_ levels
		if (loglevel >= AV_LOG_VERBOSE)
			loglevel = LOG_DEBUG;
		else if (loglevel >= AV_LOG_INFO)
			loglevel = LOG_NOTICE;
		else if (loglevel >= AV_LOG_WARNING)
			loglevel = LOG_WARNING;
		else if (loglevel >= AV_LOG_ERROR)
			loglevel = LOG_ERROR;
		else if (loglevel >= AV_LOG_FATAL)
			loglevel = LOG_CRIT;
		else
			loglevel = LOG_ALERT;
#else
		// defuse avlog log levels to be either DEBUG or ERR
		if (loglevel <= LOG_ERR)
			loglevel = LOG_ERR;
		else
			loglevel = LOG_DEBUG;
#endif
		ilogs(ffmpeg, loglevel | LOG_FLAG_LIMIT, "av_log: %s", msg);
		free(msg);
	}
}


void avc_def_init(struct codec_def_s *def) {
	// look up AVCodec structs
	if (def->avcodec_name_enc)
		def->encoder = avcodec_find_encoder_by_name(def->avcodec_name_enc);
	if (def->avcodec_name_dec)
		def->decoder = avcodec_find_decoder_by_name(def->avcodec_name_dec);
	if (def->avcodec_id >= 0) {
		if (!def->encoder)
			def->encoder = avcodec_find_encoder(def->avcodec_id);
		if (!def->decoder)
			def->decoder = avcodec_find_decoder(def->avcodec_id);
	}
	// check if we have support if we are supposed to
	if (def->avcodec_name_enc || def->avcodec_id >= 0) {
		if (def->encoder)
			def->support_encoding = 1;
	}
	if (def->avcodec_name_dec || def->avcodec_id >= 0) {
		if (def->decoder)
			def->support_decoding = 1;
	}
}


void codeclib_free(void) {
	t_hash_table_destroy(codecs_by_name_ht);
	t_hash_table_destroy(generic_ffmpeg_codecs);
	avformat_network_deinit();
	cc_cleanup();
}


bool rtpe_has_cpu_flag(enum rtpe_cpu_flag flag) {
	static bool done = false;
	static bool cpu_flags[__NUM_RTPE_CPU_FLAGS] = {false,};

	if (!done) {
#if defined(__x86_64__)
		int32_t ebx_7h0h, edx_1h;

		__asm (
			"mov $1, %%eax"		"\n\t"
			"cpuid"			"\n\t"
			"mov %%edx, %1"		"\n\t"
			"mov $7, %%eax"		"\n\t"
			"xor %%ecx, %%ecx"	"\n\t"
			"cpuid"			"\n\t"
			"mov %%ebx, %0"		"\n\t"
			: "=rm" (ebx_7h0h), "=rm" (edx_1h)
			:
			: "eax", "ebx", "ecx", "edx"
		    );

		cpu_flags[RTPE_CPU_FLAG_SSE2]      = !!(edx_1h   & (1L << 26));
		cpu_flags[RTPE_CPU_FLAG_AVX2]      = !!(ebx_7h0h & (1L << 5));
		cpu_flags[RTPE_CPU_FLAG_AVX512BW]  = !!(ebx_7h0h & (1L << 30));
		cpu_flags[RTPE_CPU_FLAG_AVX512F]   = !!(ebx_7h0h & (1L << 16));
#endif

		done = true;
	}

	if (flag < 0 || flag >= __NUM_RTPE_CPU_FLAGS)
		abort();

	return cpu_flags[flag];
}


void *dlsym_assert(void *handle, const char *sym, const char *fn) {
	void *ret = dlsym(handle, sym);
	if (!ret)
		die("Failed to resolve symbol '%s' from '%s': %s", sym, fn, dlerror());
	return ret;
}



void codeclib_register_codec(const codec_def_t *c) {
	struct codec_def_s *n = realloc(__codec_defs, sizeof(*__codec_defs) * (__num_codec_defs + 1));
	if (!n) {
		fprintf(stderr, "Out of memory initialising codecs\n");
		abort();
	}

	__codec_defs = n;

	memcpy(&__codec_defs[__num_codec_defs], c, sizeof(*c));

	__num_codec_defs++;
}


void codeclib_init(int print) {
#if LIBAVCODEC_VERSION_INT < AV_VERSION_INT(58, 9, 100)
	av_register_all();
	avcodec_register_all();
	avfilter_register_all();
#endif
	avformat_network_init();
	av_log_set_callback(avlog_ilog);

	codecs_by_name_ht = codecs_by_name_new();
	generic_ffmpeg_codecs = codecs_by_id_alloc_new();

	cc_init();

	for (unsigned int i = 0; i < __num_codec_defs; i++) {
		// add to hash table
		struct codec_def_s *def = &__codec_defs[i];
		def->rtpname_str = STR(def->rtpname);
		assert(t_hash_table_lookup(codecs_by_name_ht, &def->rtpname_str) == NULL);
		t_hash_table_insert(codecs_by_name_ht, &def->rtpname_str, def);

		// init undefined member vars
		if (!def->default_clockrate_fact.mult)
			def->default_clockrate_fact.mult = 1;
		if (!def->default_clockrate_fact.div)
			def->default_clockrate_fact.div = 1;
		if (!def->default_ptime)
			def->default_ptime = -1;
		if (!def->default_clockrate)
			def->default_clockrate = -1;
		if (!def->default_channels)
			def->default_channels = -1;

		// init RFC-related info
		const struct rtp_payload_type *pt = rtp_get_rfc_codec(&def->rtpname_str);
		if (pt)
			def->rfc_payload_type = pt->payload_type;
		else {
			// special case:
			if (!strcmp(def->rtpname, "G729a"))
				def->rfc_payload_type = 18;
			else
				def->rfc_payload_type = -1;
		}

		if (def->codec_type && def->codec_type->def_init)
			def->codec_type->def_init(def);

		if (!strcmp(def->rtpname, "CN"))
			codec_def_cn = def;
		if (def->avcodec_id == AV_CODEC_ID_PCM_S16LE)
			codec_def_pcm16 = def;

		if (print) {
			if (def->support_encoding && def->support_decoding) {
				if (def->default_channels > 0 && def->default_clockrate >= 0)
					printf("%20s: fully supported\n", def->rtpname);
				else
					printf("%20s: codec supported but lacks RTP definition\n", def->rtpname);
			}
			else if (def->support_decoding)
				printf("%20s: supported for decoding only\n", def->rtpname);
			else if (def->support_encoding)
				printf("%20s: supported for encoding only\n", def->rtpname);
			else
				printf("%20s: not supported\n", def->rtpname);
		}
		else {
			if (!def->support_encoding && !def->support_decoding)
				ilog(LOG_DEBUG, "Codec %s is not supported by codec library",
						def->rtpname);
			else if (!def->support_encoding) {
				ilog(LOG_DEBUG, "Codec %s is only supported for decoding "
						"by codec library", def->rtpname);
			}
			else if (!def->support_decoding)
				ilog(LOG_DEBUG, "Codec %s is only supported for encoding "
						"by codec library", def->rtpname);
		}

		if (def->supplemental)
			g_queue_push_tail(&__supplemental_codecs, def);

		if (rtpe_common_config_ptr->mos_type) {
			def->mos_type = rtpe_common_config_ptr->mos_type;
			if (def->mos_type == MOS_FB && def->default_clockrate != 48000)
				def->mos_type = MOS_NB;
		}
	}
}






static int ptr_cmp(const void *a, const void *b, void *dummy) {
	if (a < b)
		return -1;
	if (a > b)
		return 1;
	return 0;
}

void __packet_sequencer_init(packet_sequencer_t *ps, GDestroyNotify ffunc) {
	ps->packets = g_tree_new_full(ptr_cmp, NULL, NULL, ffunc);
	ps->seq = -1;
}
void packet_sequencer_destroy(packet_sequencer_t *ps) {
	if (ps->packets)
		g_tree_destroy(ps->packets);
	ps->packets = NULL;
}
struct tree_searcher {
	int find_seq,
	    found_seq;
};
static int packet_tree_search(const void *testseq_p, const void *ts_p) {
	struct tree_searcher *ts = (void *) ts_p;
	int testseq = GPOINTER_TO_INT(testseq_p);
	// called as a binary search test function. we're looking for the lowest
	// seq number that is higher than find_seq. if our test number is too low,
	// we proceed with higher numbers. if it's too high, we proceed to the lower
	// numbers, but remember the lowest we've seen along that path.
	if (G_UNLIKELY(testseq == ts->find_seq)) {
		// we've struck gold
		ts->found_seq = testseq;
		return 0;
	}
	if (testseq < ts->find_seq)
		return 1;
	// testseq > ts->find_seq
	if (ts->found_seq == -1 || testseq < ts->found_seq)
		ts->found_seq = testseq;
	return -1;
}
// caller must take care of locking
static void *__packet_sequencer_next_packet(packet_sequencer_t *ps, int num_wait) {
	// see if we have a packet with the correct seq nr in the queue
	seq_packet_t *packet = g_tree_lookup(ps->packets, GINT_TO_POINTER(ps->seq));
	if (G_LIKELY(packet != NULL)) {
		cdbg("returning in-sequence packet (seq %i)", ps->seq);
		goto out;
	}

	// why not? do we have anything? (we should)
	int nnodes = g_tree_nnodes(ps->packets);
	if (G_UNLIKELY(nnodes == 0)) {
		cdbg("packet queue empty");
		return NULL;
	}
	if (G_LIKELY(nnodes < num_wait)) {
		cdbg("only %i packets in queue - waiting for more", nnodes);
		return NULL; // need to wait for more
	}

	// packet was probably lost. search for the next highest seq
	struct tree_searcher ts = { .find_seq = ps->seq + 1, .found_seq = -1 };
	packet = g_tree_search(ps->packets, packet_tree_search, &ts);
	if (packet) {
		// bullseye
		cdbg("lost packet - returning packet with next seq %i", packet->seq);
		goto out;
	}
	if (G_UNLIKELY(ts.found_seq == -1)) {
		// didn't find anything. seq must have wrapped around. retry
		// starting from zero
		ts.find_seq = 0;
		packet = g_tree_search(ps->packets, packet_tree_search, &ts);
		if (packet) {
			cdbg("lost packet - returning packet with next seq %i (after wrap)", packet->seq);
			goto out;
		}
		if (G_UNLIKELY(ts.found_seq == -1))
			abort();
	}

	// pull out the packet we found
	packet = g_tree_lookup(ps->packets, GINT_TO_POINTER(ts.found_seq));
	if (G_UNLIKELY(packet == NULL))
		abort();

	cdbg("lost multiple packets - returning packet with next highest seq %i", packet->seq);

out:
	;
	uint16_t l = packet->seq - ps->seq;
	ps->lost_count += l;

	g_tree_steal(ps->packets, GINT_TO_POINTER(packet->seq));
	ps->seq = (packet->seq + 1) & 0xffff;

	unsigned int ext_seq = ps->roc << 16 | packet->seq;
	while (ext_seq < ps->ext_seq) {
		ps->roc++;
		ext_seq += 0x10000;
	}
	ps->ext_seq = ext_seq;

	return packet;
}
void *packet_sequencer_next_packet(packet_sequencer_t *ps) {
	return __packet_sequencer_next_packet(ps, 10); // arbitrary value
}
void *packet_sequencer_force_next_packet(packet_sequencer_t *ps) {
	return __packet_sequencer_next_packet(ps, 0);
}

int packet_sequencer_next_ok(packet_sequencer_t *ps) {
	if (g_tree_lookup(ps->packets, GINT_TO_POINTER(ps->seq)))
		return 1;
	return 0;
}

int packet_sequencer_insert(packet_sequencer_t *ps, seq_packet_t *p) {
	int ret = 0;

	// check seq for dupes
	if (G_UNLIKELY(ps->seq == -1)) {
		// first packet we see
		ps->seq = p->seq;
		goto seq_ok;
	}

	int diff = p->seq - ps->seq;
	// early packet: p->seq = 200, ps->seq = 150, diff = 50
	if (G_LIKELY(diff >= 0 && diff < PACKET_SEQ_DUPE_THRES))
		goto seq_ok;
	// early packet with wrap-around: p->seq = 20, ps->seq = 65530, diff = -65510
	if (diff < (-0xffff + PACKET_SEQ_DUPE_THRES))
		goto seq_ok;
	// recent duplicate: p->seq = 1000, ps->seq = 1080, diff = -80
	if (diff < 0 && diff > -PACKET_SEQ_DUPE_THRES)
		return -1;
	// recent duplicate after wrap-around: p->seq = 65530, ps->seq = 30, diff = 65500
	if (diff > (0xffff - PACKET_SEQ_DUPE_THRES))
		return -1;

	// everything else we consider a seq reset
	ilog(LOG_DEBUG, "Seq reset detected: expected seq %i, received seq %i", ps->seq, p->seq);
	ps->seq = p->seq;
	ret = 1;
	// seq ok - fall through
	g_tree_clear(ps->packets);
seq_ok:
	if (g_tree_lookup(ps->packets, GINT_TO_POINTER(p->seq)))
		return -1;
	ret = g_tree_nnodes(ps->packets) == 0 ? ret : 2; // indicates an out-of-order packet
	g_tree_insert(ps->packets, GINT_TO_POINTER(p->seq), p);

	return ret;
}




encoder_t *encoder_new(void) {
	encoder_t *ret = g_new0(__typeof(*ret), 1);
	format_init(&ret->requested_format);
	format_init(&ret->actual_format);
	ret->avpkt = av_packet_alloc();
	return ret;
}

const char *avc_encoder_init(encoder_t *enc, const str *extra_opts) {
	enc->avc.codec = enc->def->encoder;
	if (!enc->avc.codec)
		return "output codec not found";

	enc->avc.avcctx = avcodec_alloc_context3(enc->avc.codec);
	if (!enc->avc.avcctx)
		return "failed to alloc codec context";

	enc->actual_format = enc->requested_format;

#if LIBAVCODEC_VERSION_INT >= AV_VERSION_INT(61, 19, 0)
	avcodec_get_supported_config(enc->avc.avcctx, enc->avc.codec, AV_CODEC_CONFIG_SAMPLE_FORMAT, 0, (const void **) &enc->avc.sample_fmts, NULL);
#else
	enc->avc.sample_fmts = enc->avc.codec->sample_fmts;
#endif

	enc->actual_format.format = -1;
	for (const enum AVSampleFormat *sfmt = enc->avc.sample_fmts; sfmt && *sfmt != -1; sfmt++) {
		cdbg("supported sample format for output codec %s: %s",
				enc->avc.codec->name, av_get_sample_fmt_name(*sfmt));
		if (*sfmt == enc->requested_format.format)
			enc->actual_format.format = *sfmt;
	}
	if (enc->actual_format.format == -1 && enc->avc.sample_fmts)
		enc->actual_format.format = enc->avc.sample_fmts[0];
	cdbg("using output sample format %s for codec %s",
			av_get_sample_fmt_name(enc->actual_format.format), enc->avc.codec->name);

	SET_CHANNELS(enc->avc.avcctx, enc->actual_format.channels);
	DEF_CH_LAYOUT(&enc->avc.avcctx->CH_LAYOUT, enc->actual_format.channels);
	enc->avc.avcctx->sample_rate = enc->actual_format.clockrate;
	enc->avc.avcctx->sample_fmt = enc->actual_format.format;
	enc->avc.avcctx->time_base = (AVRational){1,enc->actual_format.clockrate};
	enc->avc.avcctx->bit_rate = enc->bitrate;

	if (enc->def->set_enc_options)
		enc->def->set_enc_options(enc, extra_opts);

	int i = avcodec_open2(enc->avc.avcctx, enc->avc.codec, NULL);
	if (i) {
		ilog(LOG_ERR | LOG_FLAG_LIMIT, "Error returned from libav: %s", av_error(i));
		return "failed to open output context";
	}

	if (enc->avc.avcctx->frame_size)
		enc->samples_per_frame = enc->avc.avcctx->frame_size;
	else
		enc->samples_per_frame = enc->actual_format.clockrate * enc->ptime / 1000;

	enc->samples_per_packet = enc->samples_per_frame;

	return NULL;
}

int encoder_config(encoder_t *enc, codec_def_t *def, int bitrate, int ptime,
		const format_t *requested_format, format_t *actual_format)
{
	return encoder_config_fmtp(enc, def, bitrate, ptime, NULL, requested_format, actual_format,
			NULL, NULL, NULL);
}

int encoder_config_fmtp(encoder_t *enc, codec_def_t *def, int bitrate, int ptime,
		const format_t *input_format,
		const format_t *requested_format_p, format_t *actual_format,
		struct rtp_codec_format *fmtp, const str *fmtp_string,
		const str *extra_opts)
{
	const char *err;

	err = "codec not supported";
	if (!def->codec_type)
		goto err;

	err = "failed to parse \"fmtp\"";
	if (!codec_parse_fmtp(def, fmtp, fmtp_string, &enc->format_options))
		goto err;

	// select encoder format
	format_t requested_format = *requested_format_p;
	enc->clockrate_fact = def->default_clockrate_fact;
	if (def->select_encoder_format)
		def->select_encoder_format(enc, &requested_format, input_format, fmtp);

	requested_format.clockrate = fraction_mult(requested_format.clockrate, &enc->clockrate_fact);

	// anything to do?
	if (G_LIKELY(format_eq(&requested_format, &enc->requested_format))) {
		if (!input_format)
			goto done;
		if (G_LIKELY(format_eq(input_format, &enc->input_format)))
			goto done;
	}

	encoder_close(enc);

	if (ptime <= 0)
		ptime = 20;
	if (def->minimum_ptime && ptime < def->minimum_ptime)
		ptime = def->minimum_ptime;

	enc->requested_format = requested_format;
	if (input_format)
		enc->input_format = *input_format;
	else
		format_init(&enc->input_format);
	enc->def = def;
	enc->ptime = ptime;
	enc->bitrate = bitrate;

	err = def->codec_type->encoder_init ? def->codec_type->encoder_init(enc, extra_opts) : 0;
	if (err)
		goto err;

// output frame and fifo
	enc->frame = av_frame_alloc();

	if (enc->actual_format.format != -1 && enc->actual_format.clockrate > 0) {
		enc->frame->nb_samples = enc->samples_per_frame ? : 256;
		enc->frame->format = enc->actual_format.format;
		enc->frame->sample_rate = enc->actual_format.clockrate;
		DEF_CH_LAYOUT(&enc->frame->CH_LAYOUT, enc->actual_format.channels);
		if (av_frame_get_buffer(enc->frame, 0) < 0)
			abort();

		enc->fifo = av_audio_fifo_alloc(enc->frame->format, enc->actual_format.channels,
				enc->frame->nb_samples);

		ilog(LOG_DEBUG, "Initialized encoder with frame size %u samples", enc->frame->nb_samples);
	}
	else
		ilog(LOG_DEBUG, "Initialized encoder without frame buffer");


done:
	if (actual_format)
		*actual_format = enc->actual_format;
	return 0;

err:
	encoder_close(enc);
	ilog(LOG_ERR, "Error configuring media output for codec %s: %s", def->rtpname, err);
	return -1;
}

void avc_encoder_close(encoder_t *enc) {
	if (enc->avc.avcctx) {
#if LIBAVCODEC_VERSION_INT < AV_VERSION_INT(61, 0, 0)
		avcodec_close(enc->avc.avcctx);
#endif
		avcodec_free_context(&enc->avc.avcctx);
	}
	enc->avc.avcctx = NULL;
	enc->avc.codec = NULL;
}

void encoder_close(encoder_t *enc) {
	if (!enc)
		return;
	if (enc->def && enc->def->codec_type && enc->def->codec_type->encoder_close)
		enc->def->codec_type->encoder_close(enc);
	format_init(&enc->requested_format);
	format_init(&enc->actual_format);
	av_audio_fifo_free(enc->fifo);
	av_frame_free(&enc->frame);
	enc->mux_dts = 0;
	enc->fifo = NULL;
	enc->fifo_pts = 0;
}
void encoder_free(encoder_t *enc) {
	encoder_close(enc);
	av_packet_free(&enc->avpkt);
	resample_shutdown(&enc->resampler);
	g_free(enc);
}

int avc_encoder_input(encoder_t *enc, AVFrame **frame) {
	int keep_going = 0;
	int got_packet = 0;
	int av_ret = 0;

	if (!enc->avc.avcctx)
		return -1;

#if LIBAVCODEC_VERSION_INT >= AV_VERSION_INT(57, 36, 0)
	if (*frame) {
		av_ret = avcodec_send_frame(enc->avc.avcctx, *frame);
		cdbg("send frame ret %i", av_ret);
		if (av_ret == 0) {
			// consumed
			*frame = NULL;
			keep_going = 1;
		}
		else {
			if (av_ret == AVERROR(EAGAIN))
				; // check output and maybe try again
			else
				goto err;
		}
	}

	av_ret = avcodec_receive_packet(enc->avc.avcctx, enc->avpkt);
	cdbg("receive packet ret %i", av_ret);
	if (av_ret == 0) {
		// got some data
		keep_going = 1;
		got_packet = 1;
	}
	else {
		if (av_ret == AVERROR(EAGAIN))
			; // try again if there's still more input
		else
			goto err;
	}
#else
	if (!*frame)
		return 0;

	av_ret = avcodec_encode_audio2(enc->avc.avcctx, enc->avpkt, *frame, &got_packet);
	cdbg("encode frame ret %i, got packet %i", av_ret, got_packet);
	if (av_ret == 0)
		*frame = NULL; // consumed
	else
		goto err;
	if (got_packet)
		keep_going = 1;
#endif

	if (!got_packet)
		return keep_going;

	cdbg("output avpkt size is %i", (int) enc->avpkt->size);
	cdbg("output pkt pts/dts is %li/%li", (long) enc->avpkt->pts,
			(long) enc->avpkt->dts);

	// the encoder may return frames with the same dts multiple consecutive times.
	// the muxer may not like this, so ensure monotonically increasing dts.
	if (enc->mux_dts > enc->avpkt->dts)
		enc->avpkt->dts = enc->mux_dts;
	if (enc->avpkt->pts < enc->avpkt->dts)
		enc->avpkt->pts = enc->avpkt->dts;

	return keep_going;

err:
	if (av_ret)
		ilog(LOG_ERR | LOG_FLAG_LIMIT, "Error returned from libav: %s", av_error(av_ret));
	return -1;
}

int encoder_input_data(encoder_t *enc, AVFrame *frame,
		int (*callback)(encoder_t *, void *u1, void *u2), void *u1, void *u2)
{
	enc->avpkt->size = 0;

	while (1) {
		if (!enc->def || !enc->def->codec_type)
			break;
		if (!enc->def->codec_type->encoder_input)
			break;

		int ret = enc->def->codec_type->encoder_input(enc, &frame);
		if (ret < 0)
			return -1;

		if (enc->avpkt->size) {
			// don't rely on the encoder producing steady timestamps,
			// instead keep track of them ourselves based on the returned
			// frame duration
			enc->avpkt->pts = enc->next_pts;

			if (enc->def->codec_type->encoder_got_packet)
				enc->def->codec_type->encoder_got_packet(enc);

			callback(enc, u1, u2);

			enc->next_pts += enc->avpkt->duration;
			enc->mux_dts = enc->avpkt->dts + 1; // min next expected dts

			av_packet_unref(enc->avpkt);
			enc->avpkt->size = 0;
		}

		if (ret == 0)
			break;
	}

	return 0;
}

static int encoder_fifo_flush(encoder_t *enc,
		int (*callback)(encoder_t *, void *u1, void *u2), void *u1, void *u2)
{
	while (av_audio_fifo_size(enc->fifo) >= enc->frame->nb_samples) {

		if (av_audio_fifo_read(enc->fifo, (void **) enc->frame->data,
					enc->frame->nb_samples) <= 0)
			abort();

		cdbg("output fifo pts %lu",(unsigned long) enc->fifo_pts);
		enc->frame->pts = enc->fifo_pts;

		encoder_input_data(enc, enc->frame, callback, u1, u2);

		enc->fifo_pts += enc->frame->nb_samples;
	}

	return 0;
}

int encoder_input_fifo(encoder_t *enc, AVFrame *frame,
		int (*callback)(encoder_t *, void *u1, void *u2), void *u1, void *u2)
{
	AVFrame *rsmp_frame = resample_frame(&enc->resampler, frame, &enc->actual_format);
	if (!rsmp_frame) {
		ilog(LOG_ERR | LOG_FLAG_LIMIT, "Resampling failed");
		return -1;
	}
	if (av_audio_fifo_write(enc->fifo, (void **) rsmp_frame->extended_data, rsmp_frame->nb_samples) < 0)
		return -1;
	if (rsmp_frame != frame)
		av_frame_free(&rsmp_frame);

	return encoder_fifo_flush(enc, callback, u1, u2);
}


int packetizer_passthrough(AVPacket *pkt, GString *buf, str *output, size_t num_bytes, encoder_t *enc,
		int64_t *__restrict pts, int64_t *__restrict duration)
{
	if (!pkt)
		return -1;
	if (output->len < pkt->size) {
		ilog(LOG_WARN | LOG_FLAG_LIMIT, "Output packet size too small (%zu < %i)",
				output->len, pkt->size);
		return -1;
	}
	output->len = pkt->size;
	memcpy(output->s, pkt->data, pkt->size);
	*pts = pkt->pts;
	*duration = pkt->duration;
	return 0;
}

// returns: -1 = not enough data, nothing returned; 0 = returned a packet;
// 1 = returned a packet and there's more
int packetizer_samplestream(AVPacket *pkt, GString *buf, str *input_output, size_t num_bytes,
		encoder_t *enc, int64_t *__restrict pts, int64_t *__restrict duration)
{
	// avoid moving buffers around if possible:
	// most common case: new input packet has just enough (or more) data as what we need
	if (G_LIKELY(pkt && buf->len == 0 && pkt->size >= num_bytes)) {
		*pts = pkt->pts;
		*duration = pkt->duration;
		memcpy(input_output->s, pkt->data, num_bytes);
		// any leftovers?
		if (pkt->size > num_bytes) {
			g_string_append_len(buf, (char *) pkt->data + num_bytes,
					pkt->size - num_bytes);
			*duration = fraction_mult(num_bytes * 8, &enc->clockrate_fact)
				/ enc->def->bits_per_sample;
			enc->packet_pts = pkt->pts + *duration;
		}
		input_output->len = num_bytes;
		return buf->len >= num_bytes ? 1 : 0;
	}
	// we have to move data around. append input packet to buffer if we have one
	if (pkt)
		g_string_append_len(buf, (char *) pkt->data, pkt->size);
	// do we have enough?
	if (buf->len < num_bytes)
		return -1;
	// copy requested data into provided output buffer and remove from interim buffer
	memcpy(input_output->s, buf->str, num_bytes);
	input_output->len = num_bytes;
	g_string_erase(buf, 0, num_bytes);
	// adjust output pts
	*pts = enc->packet_pts;
	*duration = fraction_mult(num_bytes * 8, &enc->clockrate_fact) / enc->def->bits_per_sample;
	enc->packet_pts += *duration;
	return buf->len >= num_bytes ? 1 : 0;
}


int codeclib_set_av_opt_int(encoder_t *enc, const char *opt, int64_t val) {
	ilog(LOG_DEBUG, "Setting ffmpeg '%s' option for '%s' to %" PRId64,
			opt, enc->def->rtpname, val);

	int ret = av_opt_set_int(enc->avc.avcctx, opt, val, AV_OPT_SEARCH_CHILDREN);
	if (!ret)
		return 0;

	ilog(LOG_WARN, "Failed to set ffmpeg '%s' option for codec '%s' to %" PRId64 ": %s",
			opt, enc->def->rtpname, val, av_error(ret));
	return -1;
}



void codeclib_key_value_parse(const str *instr, bool need_value,
		void (*cb)(str *key, str *value, void *data), void *data)
{
	if (!instr || !instr->s)
		return;

	// semicolon-separated key=value
	str s = *instr;
	str key, value;
	while (str_token_sep(&value, &s, ';')) {
		if (!str_token(&key, &value, '=')) {
			if (need_value)
				continue;
			value = STR_NULL;
		}

		// truncate whitespace
		while (key.len && key.s[0] == ' ')
			str_shift(&key, 1);
		while (key.len && key.s[key.len - 1] == ' ')
			key.len--;
		while (value.len && value.s[0] == ' ')
			str_shift(&value, 1);
		while (value.len && value.s[value.len - 1] == ' ')
			value.len--;

		if (key.len == 0)
			continue;

		cb(&key, &value, data);
	}

}



static int generic_silence_dtx(decoder_t *dec, GQueue *out, int ptime) {
	if (dec->dec_out_format.format == -1)
		return -1;
	if (!dec->avc.avpkt)
		return -1;

	if (ptime <= 0)
		ptime = 20;
	int num_samples = ptime * dec->in_format.clockrate / 1000;
	ilog(LOG_DEBUG, "pushing %i silence samples into %s decoder", num_samples, dec->def->rtpname);

	// create dummy frame, fill with silence, pretend it was returned from the decoder
	AVFrame *frame = av_frame_alloc();
	frame->nb_samples = num_samples;
	frame->format = dec->dec_out_format.format;
	frame->sample_rate = dec->dec_out_format.clockrate;
	DEF_CH_LAYOUT(&frame->CH_LAYOUT, dec->dec_out_format.channels);
	if (av_frame_get_buffer(frame, 0) < 0) {
		av_frame_free(&frame);
		return -1;
	}

	memset(frame->extended_data[0], 0, frame->linesize[0]);

	// advance PTS
	frame->pts = dec->avc.avpkt->pts;
	dec->avc.avpkt->pts += frame->nb_samples;

	g_queue_push_tail(out, frame);

	return 0;
}


static int cn_append_frame(decoder_t *dec, AVFrame *f, void *u1, void *u2) {
	GQueue *out = u1;
	g_queue_push_tail(out, f);
	return 0;
}

static int generic_cn_dtx(decoder_t *dec, GQueue *out, int ptime) {
	dec->dtx.cn.cn_dec->ptime = ptime;
	return decoder_input_data(dec->dtx.cn.cn_dec, dec->dtx.cn.cn_payload,
			dec->rtp_ts, cn_append_frame, out, NULL);
}

static int generic_cn_dtx_init(decoder_t *dec) {
	// upsample CN output to same params as output of parent codec
	format_t cn_format = dec->dest_format;
	cn_format.channels = dec->in_format.channels;
	cn_format.clockrate = dec->in_format.clockrate;
	dec->dtx.cn.cn_dec = decoder_new_fmt(codec_def_cn, 8000, 1, dec->ptime, &cn_format);
	return 0;
}

static void generic_cn_dtx_cleanup(decoder_t *dec) {
	decoder_close(dec->dtx.cn.cn_dec);
}




int format_cmp_ignore(const struct rtp_payload_type *a, const struct rtp_payload_type *b) {
	return 0;
}


void frame_fill_tone_samples(enum AVSampleFormat fmt, void *samples, unsigned int offset, unsigned int num,
		unsigned int freq, unsigned int volume, unsigned int sample_rate, unsigned int channels)
{
	switch (fmt) {
		case AV_SAMPLE_FMT_S16:
			tone_samples_int16_t(samples, offset, num, freq, volume, sample_rate, channels);
			break;
		case AV_SAMPLE_FMT_S32:
			tone_samples_int32_t(samples, offset, num, freq, volume, sample_rate, channels);
			break;
		case AV_SAMPLE_FMT_DBL:
			tone_samples_double(samples, offset, num, freq, volume, sample_rate, channels);
			break;
		case AV_SAMPLE_FMT_FLT:
			tone_samples_float(samples, offset, num, freq, volume, sample_rate, channels);
			break;
		default:
			ilog(LOG_ERR | LOG_FLAG_LIMIT, "Unsupported sample format %u", fmt);
			break;
	}
}

void frame_fill_dtmf_samples(enum AVSampleFormat fmt, void *samples, unsigned int offset, unsigned int num,
		unsigned int event, unsigned int volume, unsigned int sample_rate, unsigned int channels)
{
	switch (fmt) {
		case AV_SAMPLE_FMT_S16:
			dtmf_samples_int16_t(samples, offset, num, event, volume, sample_rate, channels);
			break;
		case AV_SAMPLE_FMT_S32:
			dtmf_samples_int32_t(samples, offset, num, event, volume, sample_rate, channels);
			break;
		case AV_SAMPLE_FMT_DBL:
			dtmf_samples_double(samples, offset, num, event, volume, sample_rate, channels);
			break;
		case AV_SAMPLE_FMT_FLT:
			dtmf_samples_float(samples, offset, num, event, volume, sample_rate, channels);
			break;
		default:
			ilog(LOG_ERR | LOG_FLAG_LIMIT, "Unsupported sample format %u", fmt);
			break;
	}
}



codec_def_t *codec_def_make_generic_av(enum AVCodecID id) {
	{
		RWLOCK_R(&generic_ffmpeg_codecs_lock);

		struct codec_def_s *ret = t_hash_table_lookup(generic_ffmpeg_codecs, GINT_TO_POINTER(id));
		if (ret)
			return ret;
	}

	{
		RWLOCK_W(&generic_ffmpeg_codecs_lock);

		struct codec_def_s *ret = t_hash_table_lookup(generic_ffmpeg_codecs, GINT_TO_POINTER(id));
		if (ret)
			return ret;

		const AVCodec *codec = avcodec_find_decoder(id);
		if (!codec)
			return NULL;

		ret = g_new(__typeof(*ret), 1);
		*ret = (__typeof(*ret)) {
			.rtpname = "generic ffmpeg codec",
			.rtpname_str = STR_CONST("generic ffmpeg codec"),
			.avcodec_id = id,
			.default_clockrate_fact = {1,1},
			.media_type = MT_AUDIO,
			.codec_type = &codec_type_avcodec,
			.decoder = codec,
			.support_decoding = 1,
			.support_encoding = 1, // just pretend
		};

		t_hash_table_insert(generic_ffmpeg_codecs, GINT_TO_POINTER(id), ret);

		return ret;
	}
}