[MEncoder-users] Processing FLV file on the fly

[James Hastings-Trew]

Eric Laurent wrote:
> Hello everyone,
>
> I would like to use mencoder to process FLV files (change key frame interval, change audio format, change speed..). 
> I use a command similar to the following:
> mencoder -quiet -speed <speed> -af channels=1 -oac mp3lame -lameopts mode=3:cbr:br=64 -srate 22050 -ovc lavc -of lavf <input.flv> -lavfopts format=flv:i_certify_that_my_video_stream_does_not_use_b_frames -lavcopts vcodec=flv:keyint=<int>:vbitrate=300 -o <output.flv>
>
> If my input is a local FLV file and my output a local FLV file, every thing is OK.
> For external video content, I would like to reduce the time needed to start FLV processing by doing this process on the fly instead of first downloading the FLV file and 
> then doing the process.
>
> If I give directly the URL as input to mencoder, I get the following error:
> mencoder -demuxer +lavf -quiet -speed 0.8 -af channels=1 -oac mp3lame -lameopts mode=3:cbr:br=64 -srate 22050 -ovc lavc -of lavf <URL> -lavfopts format=flv:i_certify_that_my_video_stream_does_not_use_b_frames -lavcopts vcodec=flv:keyint=6:vbitrate=300 -o output.flv
>
> # MEncoder 1.0rc1-4.1.1 (C) 2000-2006 MPlayer Team
> # CPU: Intel(R) Pentium(R) 4 CPU 2.80GHz (Family: 15, Model: 2, Stepping: 5)
> # CPUflags: Type: 15 MMX: 1 MMX2: 1 3DNow: 0 3DNow2: 0 SSE: 1 SSE2: 1
> # Compiled for x86 CPU with extensions: MMX MMX2 SSE SSE2
> #
> # Resolving www.youtube.com for AF_INET6...
> # Resolving www.youtube.com for AF_INET...
> # Connecting to server www.youtube.com[208.65.153.253]: 80...
> # Cache size set to 320 KBytes
> # success: format: 0  data: 0x0 - 0x0
>
> # libavformat file format detected.
> # Segmentation fault.
>
>
> I have also tried to use a named pipe as mencoder input, named pipe that I filled with a progressive download, but then I get the following error:
>
> # MEncoder 1.0rc1-4.1.1 (C) 2000-2006 MPlayer Team
> # CPU: Intel(R) Pentium(R) 4 CPU 2.80GHz (Family: 15, Model: 2, Stepping: 5)
> # CPUflags: Type: 15 MMX: 1 MMX2: 1 3DNow: 0 3DNow2: 0 SSE: 1 SSE2: 1
> # Compiled for x86 CPU with extensions: MMX MMX2 SSE SSE2
> # 
> # success: format: 0  data: 0x0 - 0x0
> # libavformat file format detected.
> # Cannot seek backward in linear streams!
> # Seek failed
> # Cannot seek backward in linear streams!
> # Seek failed
> # Cannot seek backward in linear streams!
> # Seek failed
> # Cannot seek backward in linear streams!
> # Seek failed
> # Cannot seek backward in linear streams!
> # Seek failed
> # Cannot seek backward in linear streams!
> # Seek failed
> # LAVF_header: av_find_stream_info() failed
> # ============ Sorry, this file format is not recognized/supported =============
> # === If this file is an AVI, ASF or MPEG stream, please contact the author! ===
> # Cannot open demuxer.
>
> # Exiting...
>
> Is there something I am missing?
> Is it possible to use a named pipe as mencoder input when the container format is FLV? 
> What is wrong with the direct access to the URL?
>
> Thanks in advance for your help.
>
> Eric Laurent
Does your command line work if you wget download the file first, and 
then process it? If so, then the problem is probably with asking 
mEncoder to access the file in a serial fashion - it probably cannot 
read the headers of the file that way (just my educated guess).
Also, in my experience, newer builds of mEncoder don't require that 
"i_certify_that_my_video_stream_does_not_use_b_frames" option any more. 
You'll still get the warning not to use b-frames with lavf output 
containers.