[mythtv-users] Transcoding issues. SD is fine, HD fails

belcampo belcampo at zonnet.nl
Wed Apr 14 18:34:14 UTC 2010


Neil Salstrom wrote:
> On Wed, Apr 14, 2010 at 7:44 AM, belcampo <belcampo at zonnet.nl> wrote:
>> Neil Salstrom wrote:
>>> On Wed, Apr 14, 2010 at 12:19 AM, belcampo <belcampo at zonnet.nl> wrote:
>>>
>>>> The problem probably is in the misdetection of fields vs. frames. I guess
>>>> it's 50interlaced fields, which is 25fps.
>>>> If fields are interpreted as frames you get the slow-motion effect.
>>>> I issued 1456 1457 1472 on the ffmpeg 'bug' list.
>>>> Depending on the container mp4 mkv or mpeg-ts you probably can circumvent
>>>> the situation by defining 50fps in the container, play at double-speed.
>>> This is with ATSC and not PAL.  The original files are 1080i_30, 720p_60.
>> I'm almost sure that forcing to fps 60 will solve your problems.
>> ffmpeg -i transcoded-file.ext will tell you what ffmpeg thinks what ist the
>> right speed.
>>
>> mediainfo -f transcoded-file.ext will probably tell you that video duration
>> is twice the audio-length.
>>> I also tried playback without VDPAU and it behaves the same so it does
>>> not seem to be playback related but rather how it was transcoded.
>> It reads the info from transcoded-file.ext if that's wrong, because of the
>> wrong transcoding, so will playback be wrong.
> 
> If I'm reading this correctly, you are right...
> 
> From a Transcoded file:
> 
> 
> Seems stream 0 codec frame rate differs from container frame rate:
> 1000.00 (1000/1) -> 59.92 (719/12)
> Input #0, nuv, from '1121_20100321200000.nuv':
>   Duration: 27:18:53.22, start: 67708.422000, bitrate: 127 kb/s
>     Stream #0.0: Video: mpeg4, yuv420p, 1280x720, PAR 1:1 DAR 16:9,
> 59.92 tbr, 1k tbn, 1k tbc
>     Stream #0.1: Audio: mp3, 48000 Hz, 2 channels, s16, 128 kb/s
> At least one output file must be specified
> 
> From a non-Transcoded file:
> 
> Seems stream 0 codec frame rate differs from container frame rate:
> 119.88 (120000/1001) -> 59.94 (60000/1001)
> Input #0, mpegts, from '1121_20100412200000.mpg':
>   Duration: 00:59:57.33, start: 36358.937844, bitrate: 15187 kb/s
>   Program 1
>     Stream #0.0[0x31]: Video: mpeg2video, yuv420p, 1280x720 [PAR 1:1
> DAR 16:9], 19000 kb/s, 59.94 tbr, 90k tbn, 119.88 tbc
>     Stream #0.1[0x34](eng): Audio: ac3, 48000 Hz, 5.1, s16, 448 kb/s
>     Stream #0.2[0x35](spa): Audio: ac3, 48000 Hz, stereo, s16, 192 kb/s
> At least one output file must be specified
> 
> What I'm noticing is the first line showing the container framerate....
> 
> So.... I guess the question is how do I correct this or what can be
> done to prevent this in the future?
I would try to remux the encoded with tsMuxeR to an mpeg-ts, the 
gui-version tsMuxerGUI has an option to 'hard-change' the fps in the 
container, mkvmerge, or gui-variant mmg, also has this ability, don't 
know if that will correct matters.
What do/did you use for this encoding ?
   Can I somehow tell Mythtv to play
> this at the correct rate?
No idea.
> 
> Neil
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