[mythtv-users] nuvexport ffmpeg video quality

[Paul Gardiner]

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
cover everything.

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.

Cheers,
     Paul.