[mythtv-users] Help with HDPVR and ffmpeg (slightly off topic)

[Scott Naef]

On 1/16/2013 12:11 AM, HP-mini wrote:
> On Tue, 2013-01-15 at 14:33 -0500, Scott Naef wrote:
>> I am attempting to transcode recordings made with an HDPVR.  I am using
>> Mythtv to do the capture.   I originally had trouble with playback in
>> Myth but was able to use the environment variable
>> FORCE_DTS_TIMESTAMPS=1  to get proper playback in Myth.   I am an
>> I have tried several options in FFMPEG such as  -async 1 but nothing I
>> try seems to work.  I always end  up with about 1.5 second delay in
>> video from audio.    From what I understand DTS timestamps are used to
>> decode content and offer a deterministic way to predict the number of
>> frames to decode and PTS timestamps are used to show the correct frames
>> in the correct order.   If this is true (long shot!) then I guess I need
>> a way to mux the audio and video streams using DTS not PTS.   Is this
>> way the Myth player does it?
>>
>> Version:
>>
>> ffmpeg version git-2013-01-05-7e5d4fa Copyright (c) 2000-2013 the FFmpeg
>> developers
>> Any help would be greatly appreciated.  If needed I can grab a few
>> seconds of a news clip (talking heads help to see this) and offer it up
>> somewhere.
>>
>> Thank you!
>> -Scott Naef
> With stream copying you could try options on/around:
> -vsync 1 or drop
> -copytb 1
>
> the async option has been deprecated to filter aresample
> ffmpeg stream copying is fast remuxing..
>
> If you find a place for a 30 sec clip (use "dd" carefully) I will
> attempt to find a fix.
>
>
> _______________________________________________
> mythtv-users mailing list
> mythtv-users at mythtv.org
> http://www.mythtv.org/mailman/listinfo/mythtv-users

HP-mini,

Thank you for the help.  My sample source file input.mpg is at:
https://drive.google.com/uc?id=0BzSQuUjfkFN1a191MG9acnFPc3M&export=download

My resulting output.mp4 is at:
https://drive.google.com/?tab=oo&authuser=0#folders/0BzSQuUjfkFN1OWIyNEQyRndmWG8

My ffmpeg command is:
ffmpeg  -i input.mpg -async 1 -y -vcodec libx264 -r 25 -b:v 1268k -s 512x368 -acodec libmp3lame -threads 2 output.mp4

Ouput log:
https://docs.google.com/file/d/0BzSQuUjfkFN1N0VsLXVud2tsV0E/edit


I also posted this to ffmpeg-users and got a response from Carl Eugen.   It looks like ffmpeg SHOULD handle this media just fine but it might be broken in 10.0+   He has opened a ticket that can be found here:  https://ffmpeg.org/trac/ffmpeg/ticket/2143

For now (based on his findings) I have gone back to version 8 of ffmpeg and am able to get the transcode to work using the above.   I would really like to get it to work in newer versions of ffmpeg that are faster.  I am only getting about 50fps in verion 8 and got about 80 in the nightly from the 5th.

-Scott