[mythtv-users] Alternatives to lossless transcode

John Finlay finlay at moeraki.com
Sun Sep 29 20:33:56 UTC 2013


On 9/28/2013 3:33 AM, Mark Perkins wrote:
>
>> On 28 Sep 2013, at 6:07 pm, "John Pilkington" <J.Pilk at tesco.net 
>> <mailto: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 
>>>>> <mailto: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.
>
I'm beginning to think that mythtranscode has been intentionally changed 
to still work with mythtv but to make post-processing of the losslessly 
transcoded file impossible. Even mythffmpeg can't process the cut files.

John
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