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audio: auto-add downmix filter when stereo output is requested 

When -channels 2 [default] is specified and the audio decoder used
does not support internal downmixing, automatically add a pan filter
after the decoder to downmix to stereo.

Patch by Clément Bœsch, ubitux gmail com

git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@32356 b3059339-0415-0410-9bf9-f77b7e298cf2
This commit is contained in:
cigaes 2010-09-26 08:45:40 +00:00 committed by Uoti Urpala
parent 6335de8621
commit 579d743159
1 changed files with 25 additions and 0 deletions
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25
libaf/af.c
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@ -410,6 +410,26 @@ static int fixup_output_format(af_stream_t* s)
return AF_OK;
}
/**
* Automatic downmix to stereo in case the codec does not implement it.
*/
static void af_downmix(af_stream_t* s)
{
static const char * const downmix_strs[AF_NCH + 1] = {
/* FL FR RL RR FC LF AL AR */
[3] = "pan=2:" "0.6:0:" "0:0.6:" "0.4:0.4",
[4] = "pan=2:" "0.6:0:" "0:0.6:" "0.4:0:" "0:0.4",
[5] = "pan=2:" "0.5:0:" "0:0.5:" "0.2:0:" "0:0.2:" "0.3:0.3",
[6] = "pan=2:" "0.4:0:" "0:0.4:" "0.2:0:" "0:0.2:" "0.3:0.3:" "0.1:0.1",
[7] = "pan=2:" "0.4:0:" "0:0.4:" "0.2:0:" "0:0.2:" "0.3:0.3:" "0.1:0:" "0:0.1",
[8] = "pan=2:" "0.4:0:" "0:0.4:" "0.15:0:" "0:0.15:" "0.25:0.25:" "0.1:0.1:" "0.1:0:" "0:0.1",
};
const char *af_pan_str = downmix_strs[s->input.nch];
if (af_pan_str)
af_append(s, s->first, af_pan_str);
}
/* Initialize the stream "s". This function creates a new filter list
if necessary according to the values set in input and output. Input
and output should contain the format of the current movie and the
@ -421,6 +441,7 @@ static int fixup_output_format(af_stream_t* s)
The return value is 0 if success and -1 if failure */
int af_init(af_stream_t* s)
{
struct MPOpts *opts = s->opts;
int i=0;
// Sanity check
@ -436,6 +457,10 @@ int af_init(af_stream_t* s)
// Check if this is the first call
if(!s->first){
// Append a downmix pan filter at the beginning of the chain if needed
if (s->input.nch != opts->audio_output_channels
&& opts->audio_output_channels == 2)
af_downmix(s);
// Add all filters in the list (if there are any)
if (s->cfg.list) {
while(s->cfg.list[i]){