[FFmpeg-devel] Issues with ljpeg

[Mathieu Malaterre]

Hi Reimar,

On Wed, Aug 27, 2008 at 6:07 PM, Reimar D?ffinger
<Reimar.Doeffinger at stud.uni-karlsruhe.de> wrote:
> On Wed, Aug 27, 2008 at 04:29:27PM +0200, Mathieu Malaterre wrote:
>> 2008/8/16 Michael Niedermayer <michaelni at gmx.at>:
>> > we need a patch that when applied fixes the bug and the regression tests.
>> >
>> > have you tested the RGB32 code? if not please do, i think it is buggy as well
>> > and iam not going to apply a patch that fixes one function while one above
>> > is left with the identical bug.
>> > hint: the &0x1FF
>>
>> Sorry but I do not understand how I am supposed to access this part of
>> code. There is not a single line of comment in this file. Is this
>> where 32bits image get compressed ?
>
> Exactly 48 lines above the code you changed. The only place in that file
> where "RGB32" appears ;-)
>
>> That does not even make sense,
>> since I would just discard the alpha component and reuse the other
>> branch.
>
> You can not use the code for YUV for RGB, those are different formats
> (though it does do a "pseudo YUV -> RGB"). And alpha is discarded
> anyway.

ok.

>> I tried anyway with a 32bits RGB png I had on disk:
>>
>> $ ./ffmpeg -f image2 -i fran_cut.png -f image2 -pred 6 -vcodec ljpeg
>>  /tmp/out6.ljpeg
>> ...
>> Input #0, image2, from 'fran_cut.png':
>>   Duration: 00:00:00.04, start: 0.000000, bitrate: N/A
>>     Stream #0.0: Video: png, rgb32, 256x256, 25.00 tb(r)
>> Output #0, image2, to '/tmp/out6.ljpeg':
>>     Stream #0.0: Video: ljpeg, rgb32, 256x256, q=2-31, 200 kb/s, 25.00 tb(c)
>> Stream mapping:
>>   Stream #0.0 -> #0.0
>> [ljpeg @ 0xe2e5f0]colorspace not supported in jpeg
>> Error while opening codec for output stream #0.0 - maybe incorrect
>> parameters such as bit_rate, rate, width or height
>
> Yay, so nobody _ever_ tested this?! Great.
> In mpegvideo_enc.c line 263 you can comment out the "return -1;" but I
> do not know what exactly will happen then.

Great ! At least now I can access the proper spot in ljpegenc.c.

Anyway it produces some kind of jpeg, with a bit depth of 9 (don't
ask...). I have not been able to reread with any of my usual jpeg
decompressor. I have to leave now, but I'll post back if I can
understand what is going on.

Thanks,
-- 
Mathieu