format_pcm: Correct behavior of fseek and ftell for G.722

There are twice as many samples in the same number of bytes, so redefine
some of the G.722 format functions in terms of their PCM counterparts.

Change-Id: I6a8c7352624b930a5f2d9e4857f75283fa5dd9f9

formats/format_pcm.c

@@ -91,10 +91,7 @@ static struct ast_frame *pcm_read(struct ast_filestream *s, int *whennext)
 		return NULL;
 	}
 	s->fr.datalen = res;
-	if (ast_format_cmp(s->fmt->format, ast_format_g722) == AST_FORMAT_CMP_EQUAL)
-		*whennext = s->fr.samples = res * 2;
-	else
-		*whennext = s->fr.samples = res;
+	*whennext = s->fr.samples = res;
 	return &s->fr;
 }
 
@@ -410,16 +407,11 @@ static int au_rewrite(struct ast_filestream *s, const char *comment)
 static int au_seek(struct ast_filestream *fs, off_t sample_offset, int whence)
 {
 	off_t min, max, cur;
-	long offset = 0, bytes;
+	long offset = 0;
 	struct au_desc *desc = fs->_private;
 
 	min = desc->hdr_size;
 
-	if (ast_format_cmp(fs->fmt->format, ast_format_g722) == AST_FORMAT_CMP_EQUAL)
-		bytes = sample_offset / 2;
-	else
-		bytes = sample_offset;
-
 	if ((cur = ftello(fs->f)) < 0) {
 		ast_log(AST_LOG_WARNING, "Unable to determine current position in au filestream %p: %s\n", fs, strerror(errno));
 		return -1;
@@ -436,11 +428,11 @@ static int au_seek(struct ast_filestream *fs, off_t sample_offset, int whence)
 	}
 
 	if (whence == SEEK_SET)
-		offset = bytes + min;
+		offset = sample_offset + min;
 	else if (whence == SEEK_CUR || whence == SEEK_FORCECUR)
-		offset = bytes + cur;
+		offset = sample_offset + cur;
 	else if (whence == SEEK_END)
-		offset = max - bytes;
+		offset = max - sample_offset;
 
 	if (whence != SEEK_FORCECUR) {
 		offset = (offset > max) ? max : offset;
@@ -479,6 +471,23 @@ static off_t au_tell(struct ast_filestream *fs)
 	return offset - desc->hdr_size;
 }
 
+static struct ast_frame *g722_read(struct ast_filestream *s, int *whennext)
+{
+	struct ast_frame *f = pcm_read(s, whennext);
+	*whennext = s->fr.samples = (*whennext * 2);
+	return f;
+}
+
+static int g722_seek(struct ast_filestream *fs, off_t sample_offset, int whence)
+{
+	return pcm_seek(fs, sample_offset / 2, whence);
+}
+
+static off_t g722_tell(struct ast_filestream *fs)
+{
+	return pcm_tell(fs) * 2;
+}
+
 static struct ast_format_def alaw_f = {
 	.name = "alaw",
 	.exts = "alaw|al|alw",
@@ -510,10 +519,10 @@ static struct ast_format_def g722_f = {
 	.name = "g722",
 	.exts = "g722",
 	.write = pcm_write,
-	.seek = pcm_seek,
+	.seek = g722_seek,
 	.trunc = pcm_trunc,
-	.tell = pcm_tell,
-	.read = pcm_read,
+	.tell = g722_tell,
+	.read = g722_read,
 	.buf_size = (BUF_SIZE * 2) + AST_FRIENDLY_OFFSET,
 };