[MPlayer-users] Re: How to dub a video with mencoder?

[Giacomo Comes]

On Fri, Mar 04, 2005 at 12:33:16PM +0100, Nico Sabbi wrote:
> Giacomo Comes wrote:
> 
> >On Wed, Mar 02, 2005 at 04:56:07PM -0500, D Richard Felker III wrote:
> > 
> >
> >>On Wed, Mar 02, 2005 at 10:41:26PM +0100, Dominik 'Rathann' Mierzejewski 
> >>wrote:
> >>   
> >>
> >>>On Wednesday, 02 March 2005 at 03:37, D Richard Felker III wrote:
> >>>     
> >>>
> >>>>On Wed, Mar 02, 2005 at 01:47:41AM +0100, Dominik 'Rathann' 
> >>>>Mierzejewski wrote:
> >>>>       
> >>>>
> >>>>>On Tuesday, 01 March 2005 at 12:33, R C wrote:
> >>>>>         
> >>>>>
> >>>>>>On Tue, 01 Mar 2005 12:15:01 +0100
> >>>>>>Tristan Miller <psychonaut at nothingisreal.com> wrote:
> >>>>>>
> >>>>>>           
> >>>>>>
> >>>>>>>Can you recommend a program for GNU/Linux that will output OGM
> >>>>>>>containers
> >>>>>>>             
> >>>>>>>
> >>>>>>I'm pretty sure ogmmerge is the only one.
> >>>>>>           
> >>>>>>
> >>>>>That is: encode with mencoder to AVI without sound, encode audio
> >>>>>         
> >>>>>
> >>>>Encoding without sound can break a/v sync. You'd be much better off to
> >>>>use -oac pcm or -oac copy then throw away the sound in the avi file
> >>>>when remuxing.
> >>>>       
> >>>>
> >>>What if you use -noskip and/or -mc 0?
> >>>     
> >>>
> >>No, that just makes the problem worse. -mc 0 is implied anyway by
> >>-nosound. You really have to encode some sound in order for mencoder
> >>to work right. If you hate this, just resample to 8000 hz 8bit mono
> >>pcm and it hardly uses any space or cpu time.
> >>   
> >>
> >
> >The needs to encode some sound in order for mencoder to work right
> >does apply only to avi or also to mpeg?
> > 
> >
> 
> it's the same: the sync code is in mencoder.c
> 
> >Because resample to 8000 hz 8bit mono pcm does not work if you are 
> >creating an mpeg (-of mpeg). 
> >
> 
> both toolame and lavc want 16 bit samples, not 8, and the sampling
> rates admitted in  mp2 (maybe even mp3)  are 32/44.1/48 khz IIRC

mp2 can be also 16000/22050/24000
mp3 16000/22050/24000 + 8000/11025/12000

> 
> >I imagine that if I have to encode some 
> >audio in the mpeg, I should use a low freq mp2, isn't it?
> >
> 
> muxer_mpeg  can store mp2, mp3 and ac3, so as long as the sound you send
> it is not damaged or incorrect you will hear it

I think the point was the need to encode only the video and mux later the audio stream.
Just 'mencoder -noaudio' doesn't work because of the A/V sync. So I need to encode
some audio that will be anyway discarded later. 
8000 hz 8bit mono pcm doesn't require much cpu, but cannot be used with mpeg.
I will check different sample rate/bit rate/codec for the the combination
that needs less cpu resource.

Giacomo