[mythtv] Ticket #12303: mythtranscode destroys audio

[Raymond Wagner]

On 11/17/2014 7:18 AM, Dan Wilga wrote:
> On 11/15/14 6:48 AM, Raymond Wagner wrote:
>> On 11/14/2014 7:25 AM, John Pilkington wrote:
>>> On 14/11/14 12:26, MythTV" wrote:
>>>> #12303: mythtranscode destroys audio
>>>
>>>>   Would it help to have the two files?
>>>>   34M     before.mpg
>>>>   76M     after.nuv
>>>>
>>> It's unlikely to do any harm to put them in a drop-box somewhere...
>>> ... but isn't this supposed to be about compression?
>>
>> If you want to actually perform recompression of your files, instead 
>> of simply performing a lossless cut of MPEG2 recordings, you 
>> shouldn't use mythtranscode.  You seem to be recompressing to RTJPEG 
>> for some reason, but even properly configured, mythtranscode is 
>> limited to MPEG4ASP, which is only a modest increase in 
>> compressibility over MPEG2, and you're stuck in a NUV container.
> I have to disagree with the statement regarding MPEG4 compression 
> using mythtranscode. When I record OTA using my HDHR on a 1080i 
> channel, I end up with a result that is anywhere from 7.2 to 9.8 
> Gb/hour. After going through mythtranscode to MPEG4, it ends up about 
> 3.2 Gb. Is this optimal in terms of size/quality compared to other 
> codecs? Certainly not. But it's a roughly 60% savings in disk space 
> that requires much less CPU to achieve compared to better codecs like 
> H.264. The tradeoff between CPU usage and disk savings is pretty good, 
> IMHO.

Clipping commercials and remuxing to a more efficient container would 
bring those to 4-5GB in just a few minutes of work. Regardless, using 
mythtranscode to actually transcode means you're stuck with a 
Nuppelvideo file and practically no support outside of MythTV.  Even if 
you continue to use ASP, you're still better off using something other 
than mythtranscode to accomplish that.