[FFmpeg-devel] [PATCH] pulse: set default frame_size to 4608

[Federico Simoncelli]

On Sat, Jan 4, 2014 at 1:07 PM, Michael Niedermayer <michaelni at gmx.at> wrote:
> On Sat, Jan 04, 2014 at 10:01:39AM +0100, Federico Simoncelli wrote:
>> On Sat, Jan 4, 2014 at 5:03 AM, Michael Niedermayer <michaelni at gmx.at> wrote:
>> Ok, that's what I thought, and therefore I don't think that the pts
>> should be adjusted.
>> For example, in input you have nb_samples = 1024:
>>
>> [ frame0 - frame1023 ] [ frame1024 - frame2047 ] ...
>>
>> now the encoder adds 1105 frames of side data and changes nb_samples to 1152:
>>
>> [ side data 1105 frames ] [ frame0 - frame46 ] [ frame47 - frame1198 ] ...
>>
>> currently what avcodec_decode_audio4 does is discarding the side data
>> but then adjusting the pts as if they were regular playable frames,
>> and in fact frame0 is shifted to 0.023s (in my case), while in the
>> original it's at 0.000s.
>
> how is this related to pulse ?
> can you show your "work in progress" patch? theres most
> likely a bug in it if it causes something to go wrong with the
> timestamps

My work in progress on pulse is irrelevant, you can reproduce it on master:

$ ffmpeg -loglevel debug -y -f pulse -i default -t 10 recording1.mp3
...

For the pts analysis (and the bug may as well be here) I use:

https://github.com/simon3z/FFmpeg/commit/5f5e043710dfeeee84a94286a7b421b6cc928187

(please bear with the filter name and its purpose).

$ ffmpeg -y -loglevel debug -i recording1.mp3 -af afixpts recording2.mp3
...

Now as you see, the first frame received from the filter has a pts ==
1105 (since the previous ones are side data). I think that its pts
should be 0 (in this case).

Output #0, mp3, to 'recording2.mp3':
  Metadata:
    TSSE            : Lavf55.22.102
    Stream #0:0, 0, 1/90000: Audio: mp3 (libmp3lame), 48000 Hz, stereo, s16p
Stream mapping:
  Stream #0:0 -> #0:0 (mp3 -> libmp3lame)
Press [q] to stop, [?] for help
[mp3 @ 0x2ca9320] skip 1105 samples due to side data
[mp3 @ 0x2ca9320] skip 1105/1152 samples
[Parsed_afixpts_0 @ 0x2cc6940] pts: 1105, ts: 0.0230208
[Parsed_afixpts_0 @ 0x2cc6940] Unexpected frame gap: 0.023021
(interval is 0.000000, tolerance 0.000000)
[Parsed_afixpts_0 @ 0x2cc6940] No lower gap has been found, pushing
the frame anyway
[Parsed_afixpts_0 @ 0x2cc6940] pts: 1152, ts: 0.024
[Parsed_afixpts_0 @ 0x2cc6940] pts: 2304, ts: 0.048

-- 
Federico