[vlc] transcoding with different input and output chromas

[lokidor]

Hello,

With vlc 0.9.0 from git is there a simple solution to transcode video 
with different input and output chromas ?

My platform is a Nokia Internet Tablet N810 running maemo 4.0 (based on 
linux debian) and I compiled vlc inside scratchbox.

This device has a builtin webcam TCM825x which is v4l2 compatible and 
works perfectly with the following command :

qvlc v4l2:///dev/video0:chroma="UYVY":width=320:height=240

This webcam can only output UYVY or RV16 signal, so vlc need to convert 
it to I420.

As I built ffmpeg with "--enable-swcale" vlc is supposed to use the 
libswscale library which should be able to deal with the chroma 
convertion, but when I try to trancode the video with the following command:

cvlc -vvv --color v4l2:///dev/video0:chroma="UYVY":width=320:height=240 \
--sout 
'#transcode{vcodec=mp4v,vb=384}:std{access=http,mux=ts,url=192.168.1.6:8080}' 
--ttl 12 \
--sout-ffmpeg-hurry-up --ffmpeg-hurry-up --rt-priority

 I get the following error :

"
[00000329] stream_out_transcode generic debug: source 320x240, crop 
320x240, destination 320x240, padding 320x240
[00000329] stream_out_transcode generic debug: encoder aspect is 
576000:432000
[00000355] main encoder debug: looking for encoder module: 7 candidates
[00000355] ffmpeg encoder debug: libavcodec already initialized
[00000355] ffmpeg encoder debug: found encoder MPEG-4 Video
[00000355] main encoder debug: using encoder module "ffmpeg"
[00000338] main generic debug: adding a new input
[00000338] mux_asf generic debug: adding input
[00000385] main filter debug: looking for video filter2 module: 1 candidate
[00000385] main filter warning: no video filter2 module matching "scale" 
could be loaded
"

And vlc continue failling to transcode rawvideo...

After looking at the code It seem's that vlc doesn't find the libswscale 
filter defined in "codec/ffmpeg/ffmpeg.c" (which is correctly built) and 
try to load the filter from "video_filter/scale.c".
This filter can only deal with identical input and output chroma 
formats, so it is rejected.

I tried to build vlc without swscale in order to use the ffmpeg "crop 
padd" filter but it is worst :

"
[00000632] main filter debug: looking for video filter2 module: 0 candidates
[00000632] main filter error: no video filter2 module matched "crop padd"
[00000621] stream_out_transcode generic debug: no video filter found
"

And vlc continue failling to transcode rawvideo...

Vlc doesn't find a "crop padd" filter but  "vlc --list | grep crop" give 
me croppadd...
Aflter looking at the code it seems that the missing space is the key 
point but anyway this filter (defined in "video_filter/croppadd.c") is 
not the ffmpeg filter and it can only deal with identical input and 
output chroma formats...

As I know that is possible directly with vlc 0.8.6 with the ffmpeg "crop 
padd" filter I would know why I can't with vlc 0.9  ?

Maybe vlc 0.9 uses a different method ?

I saw there is a yuy2_i420 conversion filter but I didn't find a way to 
use it on the command line.

Lokidor