[Ffmpeg-devel] cutting a file and getting still images

Cyrus A lists
Fri Nov 3 22:17:16 CET 2006 

Cyrus A wrote:
> V?ctor Paesa wrote:
>>> Hi,
>>>    
>>>> Cyrus A wrote:
>>>>      
>>>>> I'm trying to crop a 30-minute or hour-long segment of video down 
>>>>> to 1
>>>>> minute and then immediately generate 60 still frames (one for each
>>>>> second) from the resulting chopped video.
>>>>>
>>>>> Here are the commands I used:
>>>>>
>>>>> long input file generated with:
>>>>> ffmpeg -v 0 -i /dev/video0 -async 1 -y -vcodec mpeg4 -acodec mp3 -t
>>>>> 1780 -b 1750k -ab 192 -s 480x384 -r ntsc -vtag DX50
>>>>> 'long_input_file.avi'
>>>>>
>>>>> "cut" command:
>>>>> ffmpeg -ss 180 -t 60 -y -vcodec copy -acodec copy -i
>>>>> long_input_file.avi short_output_file.avi
>>>>>
>>>>> still frames generation:
>>>>> ffmpeg -i short_output_file.avi -r 1 -f image2 frame%03d.jpg
>>>>>
>>>>>
>>>>> Console output for second command:
>>>>>
>>>>> FFmpeg version SVN-r6849, Copyright (c) 2000-2006 Fabrice Bellard, et
>>>>> al.
>>>>>  configuration:  --enable-mp3lame
>>>>>  libavutil version: 49.0.2
>>>>>  libavcodec version: 51.23.0
>>>>>  libavformat version: 50.6.0
>>>>>  built on Oct 31 2006 12:55:14, gcc: 4.1.1 20060525 (Red Hat 4.1.1-1)
>>>>>
>>>>> Seems that stream 0 comes from film source: 30000.00 (30000/1) ->
>>>>> 29.97 (30000/1001)
>>>>> Input #0, avi, from 'short_output_file.avi':
>>>>>  Duration: 00:01:00.3, start: 0.000000, bitrate: 1972 kb/s
>>>>>  Stream #0.0: Video: mpeg4, yuv420p, 480x384, 29.97 fps(r)
>>>>>  Stream #0.1: Audio: mp3, 48000 Hz, stereo, 192 kb/s
>>>>> Output #0, image2, to 'frame%03d.jpg':
>>>>>  Stream #0.0: Video: mjpeg, yuvj420p, 480x384, q=2-31, 200 kb/s,  
>>>>> 1.00
>>>>> fps(c)
>>>>> Stream mapping:
>>>>>  Stream #0.0 -> #0.0
>>>>> Press [q] to stop encoding
>>>>> frame=    1 q=5.9 Lsize=       0kB time=1.0 bitrate=   0.0kbits/s
>>>>> video:22kB audio:0kB global headers:0kB muxing overhead -100.000000%
>>>>>
>>>>> Result:
>>>>>
>>>>> Only the first image (frame001.jpg) is created.
>>>>>
>>>>> Observations:
>>>>>
>>>>> The ffmpeg long file generation command works well. The file looks 
>>>>> and
>>>>> sounds good. Similarly,the "cutting" command above seems to work 
>>>>> well.
>>>>> I can get any size video from any part of the longer video with ease.
>>>>> The videos play normally in mplayer as well as DivX and WMP on
>>>>> windows.  However, it's the stills frame generation that seems 
>>>>> broken.
>>>>> Two caveats:
>>>>>
>>>>> First, if the stills generation command is run on a file that was
>>>>> "cut" using "-ss 0 -t 60" (no seek), the stills are generated
>>>>> correctly. Anything other than "-ss 0" causes problems.
>>>>>
>>>>> Second, videos recorded by an old version of ffmpeg (0.4.8 -- 
>>>>> probably
>>>>> early 2005 or late 2004) seem to be "cut" and "stills extracted"
>>>>> correctly by the series of commands above.
>>>>>
>>>>> file command output for avi recorded with "old" ffmpeg and chopped
>>>>> with rev6849:  RIFF (little-endian) data, AVI, 480 x 384, ~30 fps,
>>>>> video: DivX 4, audio: MPEG-1 Layer 3 (mono, 44100 Hz)
>>>>>
>>>>> file command output for avi recorded and chopped with rev6849: RIFF
>>>>> (little-endian) data, AVI, 480 x 384, ~30 fps, video: DivX 5, audio:
>>>>> MPEG-1 Layer 3 (stereo, 48000 Hz)
>>>>>
>>>>> I don't think the recording rate nor the DivX 4 vs DivX5 differences
>>>>> have anything to do with my problem, but I could be wrong.
>>>>>
>>>>> FILES:
>>>>>
>>>>> A file recorded with "old" ffmpeg and chopped on rev 6849 can be 
>>>>> found
>>>>> here:
>>>>>
>>>>> http://wkyt.dynalias.com/rec_with_old_chopped_with_6849.avi
>>>>>
>>>>> A file recorded with rev 6849 and chopped with rev 6849 can be found
>>>>> here:
>>>>>
>>>>> http://wkyt.dynalias.com/rec_with_6849_and_chopped_with_6849.avi
>>>>>
>>>>> Please let me know what you think of this problem. It is the very
>>>>> final step in a system I've been working on sporadically for about 9
>>>>> months. I might just take the rest of the week off if I can get this
>>>>> to work. Thanks again for your help.
>>>>>
>>>>> Cyrus
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> ffmpeg-devel mailing list
>>>>> ffmpeg-devel at mplayerhq.hu
>>>>> http://lists.mplayerhq.hu/mailman/listinfo/ffmpeg-devel
>>>>>         
>>>> Ok, apparently my last message was too long because nobody has 
>>>> responded
>>>> yet. Just do this:
>>>>
>>>> Download this file:
>>>>
>>>> http://wkyt.dynalias.com/rec_with_6849_and_chopped_with_6849.avi
>>>>
>>>> and run the following command to get 1 still frame for each second of
>>>> video:
>>>>
>>>> fmpeg -i rec_with_6849_and_chopped_with_6849.avi -r 1 -f image2
>>>> frame%03d.jpg
>>>>
>>>> Then tell me if it works.
>>>>
>>>>       
>>> No, it's not long, it is a good description (and I appreciate it).
>>>
>>>     
>> [snip]
>>  
>>> I'll rebase to your SVN-6849, configure with --enable-mp3lame, and
>>> I'll tell you how it goes.
>>>
>>>     
>>
>> Bad news, I'm not able to reproduce your problem, SVN-r6849 also
>> generates 62 frames:
>>
>> $ ./ffmpeg -i /cygdrive/n/rec_with_6849_and_chopped_with_6849.avi -r 
>> 1 -f
>> image2 frame%03d.jpg
>> FFmpeg version SVN-r6849, Copyright (c) 2000-2006 Fabrice Bellard, et 
>> al.
>>   configuration:  --enable-mp3lame --disable-shared
>>   libavutil version: 49.0.2
>>   libavcodec version: 51.23.0
>>   libavformat version: 50.6.0
>>   built on Nov  3 2006 21:46:54, gcc: 3.4.4 (cygming special) (gdc 0.12,
>> using dmd 0.125)
>>
>> Seems that stream 0 comes from film source: 30000.00 (30000/1) -> 29.97
>> (30000/1001)
>> Input #0, avi, from 
>> '/cygdrive/n/rec_with_6849_and_chopped_with_6849.avi':
>>   Duration: 00:01:00.0, start: 0.000000, bitrate: 1979 kb/s
>>   Stream #0.0: Video: mpeg4, yuv420p, 480x384, 29.97 fps(r)
>>   Stream #0.1: Audio: mp3, 48000 Hz, stereo, 192 kb/s
>> Output #0, image2, to 'frame%03d.jpg':
>>   Stream #0.0: Video: mjpeg, yuvj420p, 480x384, q=2-31, 200 kb/s,  1.00
>> fps(c)
>> Stream mapping:
>>   Stream #0.0 -> #0.0
>> Press [q] to stop encoding
>> frame=   62 q=5.5 Lsize=       0kB time=62.0 bitrate=   0.0kbits/s
>> video:1705kB audio:0kB global headers:0kB muxing overhead -100.000000%
>>
>>
>> I'm afraid your problem is platform related. If you can, try to build on
>> a different one (try "make distclean" before, just in case).
>>
>> Regards,
>> V?ctor
>> _______________________________________________
>> ffmpeg-devel mailing list
>> ffmpeg-devel at mplayerhq.hu
>> http://lists.mplayerhq.hu/mailman/listinfo/ffmpeg-devel
>>   
> This experiement was on FC5 x86_64 Athlong X2 with the latest 2.6.17 
> RPM kernel. What kernel were you using?
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel at mplayerhq.hu
> http://lists.mplayerhq.hu/mailman/listinfo/ffmpeg-devel
DOH! I must have made a mistake with the file I posted because it just 
worked for me on that file, too.

Try this file instead:

http://wkyt.dynalias.com/rec_with_6849_and_chopped_with_6849_2.avi

That file - just this minute - failed for me. Hopefully it'll fail for 
you too.

As I said in my long post, using -ss 0 to cut files seems to be ok. I 
must have done that with the first file. Sorry.

Cyrus

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