[mythtv-users] nuvexport ffmpeg video quality
lists at glidos.net
Fri May 27 18:01:26 UTC 2011
On 27/05/2011 18:23, Gavin Hurlbut wrote:
> On Fri, May 27, 2011 at 3:19 AM, Paul Gardiner <lists at glidos.net
> <mailto:lists at glidos.net>> wrote:
> If you're looking into the inner workings of nuvexport then maybe you
> know more about mythtranscode than is available in it's documentation.
> I assume, for each command above, mythtranscode is running in
> parallel, sticking raw video and audio in the pipes. Would be great
> if you could answer a couple of questions.
> 1) mythtranscode typically replaces its source file with the
> transcoded version. Does it still do that when --fifodir
> is specified?
> No, it doesn't. It provides the raw video frames on one fifo, PCM audio
> on another fifo, that is all. It is read-only for the original recording.
> 2) Is it always raw video and audio that is output to the fifos, or
> does that depend on the profile specified? If it is always
> raw then does the profile have any affect on what is produced?
> Always raw video, always full frame size, full frame rate, and YUV12
> encoded. For the audio, it's always PCM encoded audio (at whatever
> sampling rate it is in the recording), and until recently (this may have
> changed with some of JYA's tweaks), you get as many channels of PCM as
> there are audio channels in the source. I think this may have been
> changed somewhat.
> I think JYA was also working on the possibility of passing the original
> audio stream as is out the fifo, but I'm not sure if that's there or not.
Thanks very much for the info. That all makes perfect sense.
> 3) Do you know the specific transcode calls that coresponded
> to the encoder commands above?
> No. We got rid of transcode as it was getting harder to support, and
> didn't seem to have many users. Or maybe I'm misunderstanding the question
I mistyped the question. I meant to ask about the specific mythtranscode
call. In any case, I don't think I need that now: your other answers
Now I need to see if Handbrake can run from a pair of fifos, or
failing that how hard it would be to add the feature.
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