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mpg123: rework set_format code so mpg123audiodec works with decodebin/playbin

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The old code was using gst_caps_normalize() and was generally overly
complex. Simplify by picking sample rate and number of channels from
upstream and the sample format from the allowed caps. If the format caps
is a list of strins, just pick the first one. And if the srcpad isn't
linked yet, use the default format (S16).

https://bugzilla.gnome.org/show_bug.cgi?id=740195
This commit is contained in:
Carlos Rafael Giani 2015-01-03 13:06:45 +01:00 committed by Tim-Philipp Müller
parent eb89bf4030
commit 4b7a954cae
1 changed files with 112 additions and 123 deletions
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173
ext/mpg123/gstmpg123audiodec.c
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@ -438,44 +438,12 @@ gst_mpg123_audio_dec_handle_frame (GstAudioDecoder * dec,
static gboolean
gst_mpg123_audio_dec_set_format (GstAudioDecoder * dec, GstCaps * input_caps)
{
/* Using the parsed information upstream, and the list of allowed caps
* downstream, this code tries to find a suitable audio info. It is important
* to keep in mind that the rate and number of channels should never deviate
* from the one the bitstream has, otherwise mpg123 has to mix channels and/or
* resample (and as its docs say, its internal resampler is very crude). The
* sample format, however, can be chosen freely, because the MPEG specs do not
* mandate any special format. Therefore, rate and number of channels are taken
* from upstream (which parsed the MPEG frames, so the input_caps contain
* exactly the rate and number of channels the bitstream actually has), while
* the sample format is chosen by trying out all caps that are allowed by
* downstream. This way, the output is adjusted to what the downstream prefers.
*
* Also, the new output audio info is not set immediately. Instead, it is
* considered the "next audioinfo". The code waits for mpg123 to notice the new
* format (= when mpg123_decode_frame() returns MPG123_AUDIO_DEC_NEW_FORMAT),
* and then sets the next audioinfo. Otherwise, the next audioinfo is set too
* soon, which may cause problems with mp3s containing several format headers.
* One example would be an mp3 with the first 30 seconds using 44.1 kHz, then
* the next 30 seconds using 32 kHz. Rare, but possible.
*
* STEPS:
*
* 1. get rate and channels from input_caps
* 2. get allowed caps from src pad
* 3. for each structure in allowed caps:
* 3.1. take format
* 3.2. if the combination of format with rate and channels is unsupported by
* mpg123, go to (3), or exit with error if there are no more structures
* to try
* 3.3. create next audioinfo out of rate,channels,format, and exit
*/
int rate, channels;
/* "encoding" is the sample format specifier for mpg123 */
int encoding;
int sample_rate, num_channels;
GstAudioFormat format;
GstMpg123AudioDec *mpg123_decoder;
GstCaps *allowed_srccaps;
guint structure_nr;
gboolean match_found = FALSE;
gboolean retval = FALSE;
mpg123_decoder = GST_MPG123_AUDIO_DEC (dec);
@ -483,7 +451,7 @@ gst_mpg123_audio_dec_set_format (GstAudioDecoder * dec, GstCaps * input_caps)
mpg123_decoder->has_next_audioinfo = FALSE;
/* Get rate and channels from input_caps */
/* Get sample rate and number of channels from input_caps */
{
GstStructure *structure;
gboolean err = FALSE;
@ -492,52 +460,68 @@ gst_mpg123_audio_dec_set_format (GstAudioDecoder * dec, GstCaps * input_caps)
* input caps structures don't make sense */
structure = gst_caps_get_structure (input_caps, 0);
if (!gst_structure_get_int (structure, "rate", &rate)) {
if (!gst_structure_get_int (structure, "rate", &sample_rate)) {
err = TRUE;
GST_ERROR_OBJECT (dec, "Input caps do not have a rate value");
}
if (!gst_structure_get_int (structure, "channels", &channels)) {
if (!gst_structure_get_int (structure, "channels", &num_channels)) {
err = TRUE;
GST_ERROR_OBJECT (dec, "Input caps do not have a channel value");
}
if (err)
return FALSE;
if (G_UNLIKELY (err))
goto done;
}
/* Get the caps that are allowed by downstream */
/* Get sample format from the allowed src caps */
{
GstCaps *allowed_srccaps_unnorm =
GstCaps *allowed_srccaps =
gst_pad_get_allowed_caps (GST_AUDIO_DECODER_SRC_PAD (dec));
if (!allowed_srccaps_unnorm) {
GST_ERROR_OBJECT (dec, "Allowed src caps are NULL");
return FALSE;
}
allowed_srccaps = gst_caps_normalize (allowed_srccaps_unnorm);
}
/* Go through all allowed caps, pick the first one that matches */
for (structure_nr = 0; structure_nr < gst_caps_get_size (allowed_srccaps);
++structure_nr) {
GstStructure *structure;
if (allowed_srccaps == NULL) {
/* srcpad is not linked (yet), so no peer information is available;
* just use the default sample format (16 bit signed integer) */
GST_DEBUG_OBJECT (mpg123_decoder,
"srcpad is not linked (yet) -> using S16 sample format");
format = GST_AUDIO_FORMAT_S16;
encoding = MPG123_ENC_SIGNED_16;
} else {
gchar const *format_str;
GstAudioFormat format;
int encoding;
GValue const *format_value;
structure = gst_caps_get_structure (allowed_srccaps, structure_nr);
/* Look at the sample format values from the first structure */
GstStructure *structure = gst_caps_get_structure (allowed_srccaps, 0);
format_value = gst_structure_get_value (structure, "format");
format_str = gst_structure_get_string (structure, "format");
if (format_str == NULL) {
GST_DEBUG_OBJECT (dec, "Could not get format from src caps");
continue;
if (GST_VALUE_HOLDS_LIST (format_value)) {
/* if value is a format list, pick the first entry */
GValue const *fmt_list_value =
gst_value_list_get_value (format_value, 0);
format_str = g_value_get_string (fmt_list_value);
} else if (G_VALUE_HOLDS_STRING (format_value)) {
/* if value is a string, use it directly */
format_str = g_value_get_string (format_value);
} else {
GST_ERROR_OBJECT (mpg123_decoder,
"format value in caps structure %" GST_PTR_FORMAT
" is of invalid type (must be plain string or string list)",
structure);
format_str = NULL;
}
format = GST_AUDIO_FORMAT_UNKNOWN;
/* get the format value from the string */
if (G_LIKELY (format_str != NULL)) {
format = gst_audio_format_from_string (format_str);
if (format == GST_AUDIO_FORMAT_UNKNOWN) {
GST_DEBUG_OBJECT (dec, "Unknown format %s", format_str);
continue;
if (G_UNLIKELY (format == GST_AUDIO_FORMAT_UNKNOWN)) {
GST_ERROR_OBJECT (mpg123_decoder, "format \"%s\" is invalid",
format_str);
}
}
/* convert format to mpg123 encoding */
if (G_LIKELY (format != GST_AUDIO_FORMAT_UNKNOWN)) {
switch (format) {
case GST_AUDIO_FORMAT_S16:
encoding = MPG123_ENC_SIGNED_16;
@ -563,39 +547,44 @@ gst_mpg123_audio_dec_set_format (GstAudioDecoder * dec, GstCaps * input_caps)
default:
GST_DEBUG_OBJECT (dec,
"Format %s in srccaps is not supported", format_str);
continue;
goto done;
}
{
int err;
/* Cleanup old formats & set new one */
mpg123_format_none (mpg123_decoder->handle);
err = mpg123_format (mpg123_decoder->handle, rate, channels, encoding);
if (err != MPG123_OK) {
GST_DEBUG_OBJECT (dec,
"mpg123 cannot use caps %" GST_PTR_FORMAT
" because mpg123_format() failed: %s", structure,
mpg123_strerror (mpg123_decoder->handle));
continue;
}
}
gst_audio_info_init (&(mpg123_decoder->next_audioinfo));
gst_audio_info_set_format (&(mpg123_decoder->next_audioinfo), format, rate,
channels, NULL);
GST_LOG_OBJECT (dec, "The next audio format is: %s, %u Hz, %u channels",
format_str, rate, channels);
mpg123_decoder->has_next_audioinfo = TRUE;
match_found = TRUE;
break;
}
gst_caps_unref (allowed_srccaps);
}
}
return match_found;
/* Sample rate, number of channels, and sample format are known at this point.
* Set the audioinfo structure's values and the mpg123 format. */
{
int err;
/* clear all existing format settings from the mpg123 instance */
mpg123_format_none (mpg123_decoder->handle);
/* set the chosen format */
err =
mpg123_format (mpg123_decoder->handle, sample_rate, num_channels,
encoding);
if (err != MPG123_OK) {
GST_WARNING_OBJECT (dec,
"mpg123_format() failed: %s",
mpg123_strerror (mpg123_decoder->handle));
} else {
gst_audio_info_init (&(mpg123_decoder->next_audioinfo));
gst_audio_info_set_format (&(mpg123_decoder->next_audioinfo), format,
sample_rate, num_channels, NULL);
GST_LOG_OBJECT (dec, "The next audio format is: %s, %u Hz, %u channels",
gst_audio_format_to_string (format), sample_rate, num_channels);
mpg123_decoder->has_next_audioinfo = TRUE;
retval = TRUE;
}
}
done:
return retval;
}