[mythtv-users] Alternatives to lossless transcode

[Mark Perkins]

>> On 28 Sep 2013, at 6:07 pm, "John Pilkington" <J.Pilk at tesco.net> wrote:
>> 
>> On 28/09/13 04:26, Mark Perkins wrote:
>> 
>>>> On 28 Sep 2013, at 3:58 am, "John Finlay" <finlay at moeraki.com> wrote:
>>>> 
>>>>> On 9/27/2013 11:11 AM, Raymond Wagner wrote:
>>>>> On 9/27/2013 12:40 PM, John Finlay wrote:
>>>>> Since lossless transcode in 0.27 seems broken in my tests what alternatives do you use to losslessly cut out commercials, etc.?
>>>> 
>>>> Is this a recent issue?  It was working fine for me a few months back on the 0.27 developmental builds.
>>> 
>>> Recent for me since I just upgraded to 0.27 and tried the lossless transcode. For example the original file is seen by ffmpeg like:
>>> 
>>> Input #0, mpegts, from '1071_20130925050000.mpg':
>>> Duration: 00:59:57.84, start: 8442.162544, bitrate: 10573 kb/s
>>>   Stream #0.0[0x31]: Video: mpeg2video (Main), yuv420p, 1920x1080 [PAR 1:1 DAR 16:9], 13216 kb/s, 29.97 fps, 29.97 tbr, 90k tbn, 59.94 tbc
>>>   Stream #0.1[0x34](eng): Audio: ac3, 48000 Hz, 5.1, s16, 384 kb/s
>>>   Stream #0.2[0x35](spa): Audio: ac3, 48000 Hz, mono, s16, 128 kb/s (visual impaired)
>>> 
>>> and after the lossless transcode:
>>> 
>>> Input #0, mpeg, from '1071_20130925050000.mpg':
>>> Duration: 37:10:28.62, start: 0.316133, bitrate: 191 kb/s
>>>   Stream #0.0[0x1e0]: Video: mpeg2video (Main), yuv420p, 1920x1080 [PAR 1:1 DAR 16:9], 13216 kb/s, 29.97 fps, 29.97 tbr, 90k tbn, 59.94 tbc
>>>   Stream #0.1[0x80]: Audio: ac3, 48000 Hz, 5.1, s16, 384 kb/s
>>>   Stream #0.2[0x81]: Audio: ac3, 48000 Hz, mono, s16, 128 kb/s (visual impaired)
> 
>> [Mark] I had that exact problem on 0.26 (I assume by lossless transcode you mean mythtranscode). Searching previous threads I couldn't find a solution although there did seem to be a small number of people with the same issue. I gave up (after 100's of hrs of testing different things - I just couldn't nail it down) and ended up moving to dvbcut (I think it's called from memory) with the projectx cut switch. Note that dvbcut is not frame accurate. I haven't re-tried since moving to 0.27 but it is on the list of things to do. I also tried lossless_cut but always ended up with audio / video out of sync.
> 
> It wasn't clear to me what bad effects you were seeing, although clearly ffmpeg has a problem with the final bitrate.
[Mark] Yes, I didn't specify. I think it is actually mostly now getting covered in the other thread (http://www.mythtv.org/pipermail/mythtv-users/2013-September/354074.html)- but incorrect bit rate and subsequent processing failing. On a file that had commercials cut using mythtranscode:
- ProjectX would terminate randomly at one of the cuts and only partially output.
- Handbrake would occasionally (1 in 3) output a file with no video
- AVIDemux would produce file with audio / video sync progressively deteriorating. 25min show with only 2 cuts was not too bad but by the end of a 2hr movie with lots of commercials it might be nearly 1sec different.
If I recall correctly MythTV would play the mythtranscoded file with no issue, it was only post processing that caused all the headaches although as said before the bit rate metadata appeared corrupted.

> Mark may have been referring to my script at http://www.mythtv.org/wiki/MythDVBcut,

[Mark] Correct.

> but that apparently needs to be configured to create MKV output if used with HD mpeg2 recordings.  You might find this link useful, though.  I haven't seen an update.
> 
> http://www.gossamer-threads.com/lists/mythtv/users/547560#547560
> 
> John P
> 
> 
> 
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