[mythtv] Ticket #12303: mythtranscode destroys audio

Raymond Wagner raymond at wagnerrp.com
Tue Nov 18 05:36:43 UTC 2014

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, 

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.

More information about the mythtv-dev mailing list