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swr/swresample: avoid reapplication of firstpts 

During a resampling operation where

1) user has specified first_pts
2) SWR_FLAG_RESAMPLE is not set initially (directly or otherwise)
3) first_pts has been fulfilled (always using hard compensation)

then upon first encountering a delay where a soft compensation is
required, swr_set_compensation will lead to another init of swr which
will reset outpts to the specified firstpts thus leading to an output
frame having its pts = firstpts. When the next input frame is received,
swr will see a large delay and inject silence from firstpts to the
current frame's pts. This can lead to severe desync and in worst case,
loss of audio playback.

Parameter firstpts initialized to AV_NOPTS_VALUE in swr_alloc and then
checked in swr_init to avoid resetting outpts, thus avoiding reapplication
of firstpts.

Fixes #4131.
This commit is contained in:
Gyan Doshi 2023-12-15 12:16:39 +05:30
parent 2ad0b8e0ea
commit be8a4f80b9
4 changed files with 31 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
libswresample/options.c
View File

@ -171,6 +171,7 @@ av_cold struct SwrContext *swr_alloc(void){
if(s){
s->av_class= &av_class;
av_opt_set_defaults(s);
s->firstpts = AV_NOPTS_VALUE;
}
return s;
}

5
libswresample/swresample.c
View File

@ -375,8 +375,9 @@ av_cold int swr_init(struct SwrContext *s){
if (s->firstpts_in_samples != AV_NOPTS_VALUE) {
if (!s->async && s->min_compensation >= FLT_MAX/2)
s->async = 1;
s->firstpts =
s->outpts = s->firstpts_in_samples * s->out_sample_rate;
if (s->firstpts == AV_NOPTS_VALUE)
s->firstpts =
s->outpts = s->firstpts_in_samples * s->out_sample_rate;
} else
s->firstpts = AV_NOPTS_VALUE;

3
tests/fate/libswresample.mak
View File

@ -1082,6 +1082,9 @@ $(call CROSS_TEST,$(SAMPLERATES_LITE),ARESAMPLE_EXACT_LIN_ASYNC,s32p,s32le,s16)
$(call CROSS_TEST,$(SAMPLERATES_LITE),ARESAMPLE_EXACT_LIN_ASYNC,fltp,f32le,s16)
$(call CROSS_TEST,$(SAMPLERATES_LITE),ARESAMPLE_EXACT_LIN_ASYNC,dblp,f64le,s16)
FATE_SWR_RESAMPLE-$(call FILTERDEMDEC, ARESAMPLE ASETPTS ATRIM SINE, , PCM_S16LE, LAVFI_INDEV) += fate-swr-async-firstpts
fate-swr-async-firstpts: CMD = framecrc -auto_conversion_filters -copyts -f lavfi -i "sine=r=1000:samples_per_frame=100,asetpts=PTS+S+S*floor(ld(1)/4)+st(1\,ld(1)+1)*0,atrim=end=2" -filter:a aresample=async=300:first_pts=0
FATE_SWR_RESAMPLE-$(call FILTERDEMDECENCMUX, ARESAMPLE, WAV, PCM_S16LE, PCM_S16LE, WAV) += $(FATE_SWR_RESAMPLE)
fate-swr-resample: $(FATE_SWR_RESAMPLE-yes)
FATE_SWR += $(FATE_SWR_RESAMPLE-yes)

24
tests/ref/fate/swr-async-firstpts Normal file
View File

@ -0,0 +1,24 @@
#tb 0: 1/1000
#media_type 0: audio
#codec_id 0: pcm_s16le
#sample_rate 0: 1000
#channel_layout_name 0: mono
0, 0, 0, 132, 264, 0xc2981f45
0, 132, 132, 68, 136, 0xe78e468d
0, 200, 200, 100, 200, 0xd55c67d0
0, 300, 300, 100, 200, 0xd55c67d0
0, 400, 400, 100, 200, 0xd55c67d0
0, 500, 500, 93, 186, 0x85ca5db4
0, 593, 593, 110, 220, 0xa2655d0b
0, 703, 703, 108, 216, 0x95cb6f01
0, 811, 811, 108, 216, 0xf35668b8
0, 919, 919, 149, 298, 0xc273245f
0, 1068, 1068, 136, 272, 0xedeb6e0a
0, 1204, 1204, 98, 196, 0xea18668e
0, 1302, 1302, 98, 196, 0x412861e7
0, 1400, 1400, 98, 196, 0x7ec361b2
0, 1498, 1498, 110, 220, 0xf3ae6a6a
0, 1608, 1608, 108, 216, 0xab2f6c93
0, 1716, 1716, 107, 214, 0x50de6eb9
0, 1823, 1823, 106, 212, 0x67b8656d
0, 1929, 1929, 18, 36, 0x2b7911c6