[Ffmpeg-devel] Decoding images (jpeg) from an url

[Michel Bardiaux]

Stefan Lucke wrote:
> On Dienstag, 20. September 2005 10:43, Michel Bardiaux wrote:
> 
>>Stefan Lucke wrote:
>>
>>>On Montag, 19. September 2005 15:00, Michel Bardiaux wrote:
>>>
>>>
>>>>Stefan Lucke wrote:
> 
> 
>>>>>FfmpegIO: url(http://w.x.y.z:9001/disk/photo/O2385(1536x1024,0).jpg) is NOT playable (nil) (rc = -6)
>>>>>
>>>>>It works fine for mp3 urls and with stuttering audio and video for vdr files.
>>>>>FfmpegIO: url(http://w.x.y.z:9001/disk/music/O562.mp3) is playable 0x87a51c0 (rc = 0)
>>>>>FfmpegIO: url(http://w.x.y.z:9001/disk/video/O4712.vdr) is playable 0x8720de0 (rc = 0)
>>>>>
>>>>>Would be nice if some could give me a hint how to proceed.
>>>>>
>>>>>
>>>>
>>>>Since we cat access the URLs in question, and anyway the program as 
>>>>published is incomplete, I can only suggest you look in the source the 
>>>>reasons why av_open_input_file can return -6.
>>>>
>>>
>>>
>>>I think its the same as I get when calling ffmpeg:
>>>stefan at jarada:~> ffmpeg -i 'http://w.x.y.z:9001/disk/photo/O2385(1536x1024,0).jpg' x.yuv
>>>ffmpeg version CVS, build 3276800, Copyright (c) 2000-2004 Fabrice Bellard
>>>  configuration:  --enable-shared --enable-pp --enable-shared-pp --enable-gpl --enable-a52
>>>  built on Sep 17 2005 13:23:03, gcc: 3.3.1 (SuSE Linux)
>>>http://w.x.y.z:9001/disk/photo/O2385(1536x1024,0).jpg: Unknown format
>>
>>Good idea. Now we know your software is probably not to blame.
>>
>>
>>>(real ip adresses replaced).
>>>
>>
>>What happens if you try with some JPEG on the web at some URL anyone can 
>>access? (I could try that myself but you wisely asked for *hints*...)
> 
> 
> stefan at jarada:~> ffmpeg -i 'http://softdevice.berlios.de/vdr-1.3.7-vidix-radeon-alpha-screenshot-small.jpg' x.yuv
> ffmpeg version CVS, build 3276800, Copyright (c) 2000-2004 Fabrice Bellard
>   configuration:  --enable-shared --enable-pp --enable-shared-pp --enable-gpl --enable-a52
>   built on Sep 17 2005 13:23:03, gcc: 3.3.1 (SuSE Linux)
> http://softdevice.berlios.de/vdr-1.3.7-vidix-radeon-alpha-screenshot-small.jpg: Unknown format
> 
> stefan at jarada:~> ffmpeg -i 'http://softdevice.berlios.de/vdr-1.3.7-xv-screenshot-small.png' x.yuv
> ffmpeg version CVS, build 3276800, Copyright (c) 2000-2004 Fabrice Bellard
>   configuration:  --enable-shared --enable-pp --enable-shared-pp --enable-gpl --enable-a52
>   built on Sep 17 2005 13:23:03, gcc: 3.3.1 (SuSE Linux)
> http://softdevice.berlios.de/vdr-1.3.7-xv-screenshot-small.png: Unknown format
> 
> As that shows the same return code for different picture formats, I'll
> guess there is something wrong in my expectation that av_open_input_file()
> could be used as a generic approach for guessing required codec for a given
> input source.
> 
AAMOF you get the same 'Unknown format' with a plain .jpg file:

ffmpeg -i s000.jpg
ffmpeg version CVS, build 3276800, Copyright (c) 2000-2004 Fabrice Bellard
   configuration:  --enable-mp3lame --disable-strip --enable-amr_nb 
--enable-a52 --enable-gpl --enable-amr_wb --disable-shared
   built on Sep 21 2005 09:53:05, gcc: 2.95.4 20011002 (Debian prerelease)
s000.jpg: Unknown format

Seems the part of libavformat that should grok the format from the 
extension is completely broken now. Even b0rken :-) Even worse:

ffmpeg -img jpeg -i s000.jpg
ffmpeg version CVS, build 3276800, Copyright (c) 2000-2004 Fabrice Bellard
   configuration:  --enable-mp3lame --disable-strip --enable-amr_nb 
--enable-a52 --enable-gpl --enable-amr_wb --disable-shared
   built on Sep 21 2005 09:53:05, gcc: 2.95.4 20011002 (Debian prerelease)
Unknown image format: 'jpeg'

And no wonder: in libavformat/allformats.c, a lot of image formats are 
under 'if 0'. This does not look good.

At this point, there is no reason to trust the doc more than the source, 
so I need help from all the people who have recently contributed to the 
handling of single-images: give me rules or examples of commands that 
*should* work, and should be added to regression.sh (which does not seem 
to test jpeg decoding, which is probably why this was not detected)

HaND,
-- 
Michel Bardiaux
R&D Director
T +32 [0] 2 790 29 41
F +32 [0] 2 790 29 02
E mailto:mbardiaux at mediaxim.be

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