[MPlayer-users] pvr options

[Ivo]

On Wednesday 13 December 2006 17:12, Colin Brace wrote:
> Hi all,
>
> I am doing some experiments with a recently acquired PVR-150 card. The
> man page lists various options under "-pvr", audio/ video formats,
> audio/video encoding rates, and so forth, but it is unclear to me what
> the relationship is between the -pvr options and the -oac -ovc codec
> options.
>
> For example if I try something like this:
>
> mencoder				\
> /dev/video1 			\
> -pvr vbitrate=1000 abitrate=192			\
> -o out.avi			\
> pvr://
>
> which, according to the man page, will use the default MPEG-2 PS for
> video and MPEG Layer 2 for audio, mencoder returns error messages:
>
> No audio encoder (-oac) selected.
> No video encoder (-ovc) selected.
>
> If I add -oac and -ovc parameters, like this:
>
> mencoder				\
> /dev/video1 			\
> -oac copy				\
> -ovc copy				\
> -pvr vbitrate=1000 abitrate=192			\
> -ffourcc DX50		\
> -o out.avi			\
> pvr://
>
> It works, except that the -pvr options have no bearing on the output
> quality:
>
> Video bitrate: ...... 6031 kbs
> Audio bitrate: ...... 384 kbs
>
> What I am failing to understand here?

-oac/-ovc copy means you copy the raw input stream and mux it into the 
output container. There is no re-encoding done, so basically you put an 
mpeg-2 ps stream in an avi contain (not mpeg-4, so -ffourcc is wrong here).

-pvr vbitrate is specified in Mbps. Capturing, for example, a dvd compatible 
mpeg-2 stream to an mpeg-container at 1Mbps with 192kbps audio should go 
something like this:

mencoder -oac copy -ovc copy -pvr vbitrate=1:abitrate=192:fmt=dvd \
-of mpeg -mpegopts format=dvd:tsaf -o capture.mpg pvr://

If you want to re-encode to mpeg-4 w/ mp3 sound on-the-fly:

mencoder -oac lavc -ovc lavc \
-lavcopts acodec=mp3:abitrate=128:vcodec=mpeg4:vbitrate=900 \
-of avi -o capture.avi -ffourcc xvid pvr://

Note that I do not have a pvr card so I did not test these command lines, 
but this is basically how it should work. Also note that if you want to 
specify multiple sub-options (e.g. to -pvr) they are concatenated and 
separated by ':'

For fine-tuning the re-encoding process, you can have a look at the online 
documentation.

--Ivo