[FFmpeg-user] video delay after audio fix

funtastic officemab at gmail.com
Mon Mar 5 19:28:44 CET 2012

Am 5. März 2012 01:01 schrieb Andrey Utkin <andrey.krieger.utkin at gmail.com>:

> Hi Martin.
> We're glad to be helpful for ffmpeg users.
> But from my point you have described many different issues, not
> closely related to each other. It makes hard to understand you and to
> help you.
> From your first post, i got the only thing that there's no player that
> plays your video correctly (you mentioned Totem, VLC, FFplay and all
> they do not give required behaviour). I assume there's sth wrong with
> your file.
> You can fix the file by cutting the earlier-starting stream - audio,
> in your case.
> It will require you to split file into separate files - audio only and
> video only, then cutting beginning from audio file, then joining back.
> It will be simple ffmpeg commands. If you have difficulties with
> making up these commands, post here.
> --
> Andrey Utkin
> _______________________________________________
> ffmpeg-user mailing list
> ffmpeg-user at ffmpeg.org
> http://ffmpeg.org/mailman/listinfo/ffmpeg-user

hi again. You are right the question is too abstract...
so I try to precise the whole thing:

The problem can be narrowed down to one specific "problem" regarding
the download of a RTSP stream from a Wowza server (if this should be
relevant to solve the problem).

For this task I use:

ffmpeg -i rtsp:// -vcodec copy
-acodec copy -ss 0.0001 -t 30 -y share.mp4

(please see the output from the mailing thread... I posted everything)

Two explanations:
1. I have to use -vcodec copy and -acodec copy because I don't want to
encode the video during download in order to achieve the intended framerate
(on a very weak computer)
2. -ss 0.0001 is a hack to overcome problems with bad timestamps at the
beginning of the video... (shame on me...)

Please take this 2 things as necessary.

When I run the command everything works fine but the ffmpeg output shows
one particualar line:

Stream #0.0: Video: ![0][0][0] / 0x0021, yuv420p, 240x160, q=2-31, 24 tbn,
24 tbc

(I posted the complete console output earlier)

Since I believe that this line is the reason for all further problems I
would like to know how the ffmpeg command from before can be used to
specify a certain format (instead of getting this format list...)

Remember: i have to use -vcodec copy / -acodec copy...

It would be ok to tunnel the stream via http or anything else... I only
want to download the stream with as minimal encoding effort as possible
(-vcodec copy/ -acodec copy has given the best results for weak hardware so

I really appreciate every tipp or hint to support my idea.... but I don't
know if this is possible... I really hope that the question is obvious this


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