[FFmpeg-user] Problems with AC3

Richard Kimberly Heck rikiheck at lyx.org
Tue Sep 14 22:27:48 EEST 2021

On 9/14/21 12:20 PM, Paul B Mahol wrote:
> On Tue, Sep 14, 2021 at 4:52 PM Richard Kimberly Heck <rikiheck at lyx.org>
> wrote:
>> Hi, all,
>> I've recently started experiencing problems when convering files with
>> AC3 video. Basically, I end up with no sound. Here's an example. This
>> file reports as:
>> Input #0, mpeg, from 'vobfile.vob':
>>     Duration: 01:26:05.22, start: 0.233567, bitrate: 4943 kb/s
>>     Stream #0:0[0x1e0]: Video: mpeg2video (Main), yuv420p(tv, smpte170m,
>> progressive), 720x480 [SAR 32:27 DAR 16:9], 29.97 fps, 59.94 tbr, 90k
>> tbn, 59.94 tbc
>>       Side data:
>>         cpb: bitrate max/min/avg: 9800000/0/0 buffer size: 1835008
>> vbv_delay: N/A
>>     Stream #0:1[0x80]: Audio: ac3, 48000 Hz, 5.1(side), fltp, 448 kb/s
>> I try to convert it to mp4 with:
>> ffmpeg -i vobfile.vob -f mp4 -b:v 2500k -vcodec libx264 -b:a 192k
>> -aspect 16:9 -sn -y vobfile.mp4
>> and I get a file with no sound or (in other cases) only with very choppy
>> sound that is unintelligible. It's only with AC3 input that this seems
>> to be happening.
>> Are there other options I can try?
> Make sure that ac3 you want to transcode  is playing/decoding fine in
> ffplay first.

Well, I guess that is the problem. None of them seem to play right, 
though they work fine in vlc.

Anything else to do? These streams come from commercial DVDs I'm ripping 
to my media server, so they should (?) be all right. Right?


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