Prevent pixel conversion during mencoder command

[reising1]

I have the following mencoder command

mencoder -ss 0 -endpos 35 Movie.avi -oac pcm -ovc lavc -lavcopts vcodec=dvvideo:vbitrate=28771224 -ffourcc dvsd -o works.avi

Which results in the following output

Encoder SVN-r35910-4.2.1 (C) 2000-2013 MPlayer Team
success: format: 0  data: 0x0 - 0x5e009c00
libavformat version 54.61.104 (internal)
AVI file format detected.
AVI: ODML: Building ODML index (1 superindexchunks).
AVI_NI: No video stream found.
libavformat file format detected.
[lavf] stream 0: video (dvvideo), -vid 0
[lavf] stream 1: audio (pcm_s16le), -aid 0
[lavf] stream 2: audio (pcm_s16le), -aid 1
VIDEO:  [dvsd]  720x480  0bpp  29.970 fps  28771.2 kbps (3512.1 kbyte/s)
[V] filefmt:35  fourcc:0x64737664  size:720x480  fps:29.970  ftime:=0.0334
==========================================================================
Opening audio decoder: [pcm] Uncompressed PCM audio decoder
AUDIO: 32000 Hz, 2 ch, s16le, 1024.0 kbit/100.00% (ratio: 128000->128000)
Selected audio codec: [pcm] afm: pcm (Uncompressed PCM)
==========================================================================
libavcodec version 54.91.102 (internal)
Opening video filter: [expand osd=1]
Expand: -1 x -1, -1 ; -1, osd: 1, aspect: 0.000000, round: 1
==========================================================================
Opening video decoder: [ffmpeg] FFmpeg's libavcodec codec family
Selected video codec: [ffdv] vfm: ffmpeg (FFmpeg DV)
==========================================================================
Forcing output FourCC to 64737664 [dvsd].
Could not find matching colorspace - retrying with -vf scale...
Opening video filter: [scale]
Movie-Aspect is 1.33:1 - prescaling to correct movie aspect.
[swscaler @ 0x10c767640]BICUBIC scaler, from yuv411p to yuv420p using MMXEXT
videocodec: libavcodec (720x480 fourcc=64737664 [dvsd])
[dvvideo @ 0x10c7583e0]Found no DV profile for 720x480 yuv420p video. Valid DV profiles are:
[dvvideo @ 0x10c7583e0]Frame size: 720x480; pixel format: yuv411p, framerate: 30000/1001
[dvvideo @ 0x10c7583e0]Frame size: 720x576; pixel format: yuv420p, framerate: 25/1
[dvvideo @ 0x10c7583e0]Frame size: 720x576; pixel format: yuv411p, framerate: 25/1
[dvvideo @ 0x10c7583e0]Frame size: 720x480; pixel format: yuv422p, framerate: 30000/1001
[dvvideo @ 0x10c7583e0]Frame size: 720x576; pixel format: yuv422p, framerate: 25/1
[dvvideo @ 0x10c7583e0]Frame size: 1280x1080; pixel format: yuv422p, framerate: 30000/1001
[dvvideo @ 0x10c7583e0]Frame size: 1440x1080; pixel format: yuv422p, framerate: 25/1
[dvvideo @ 0x10c7583e0]Frame size: 960x720; pixel format: yuv422p, framerate: 60000/1001
[dvvideo @ 0x10c7583e0]Frame size: 960x720; pixel format: yuv422p, framerate: 50/1
[dvvideo @ 0x10c7583e0]Frame size: 720x576; pixel format: yuv420p, framerate: 25/1
Could not open codec.
FATAL: Cannot initialize video driver.

As you can see, I'm having a problem becase the pixel format is not yuv411p (otherwise I would be fine converting to dvsd because I currently have 720x480). But you'll also notice that before Mencoder tries to execute the command, it uses an swscaler BICUBIC scaler to convert my pixel format from yuv411p to yuv420p (this is part of the output above):

[swscaler @ 0x10c767640]BICUBIC scaler, from yuv411p to yuv420p using MMXEXT

In other words, it seems I started off with yuv411p, mencoder converted me to yuv420p, and because of that, I now cannot convert to dvsd.


How can I prevent mencoder from putting me into yuv420p, and why is it doing this anyways? Why can't I stay in yuv411p.

[Selur]

a. not sure if the ffdvvideo codec supports yuv411p
b. you can try adding "-vf scale, format=yv411p" (for ffmpeg '-pix_fmt ...')
c. if that doesn't help forcing no aspect ratio "-noaspect" or forcing a specific aspect ration "-aspect 4:3" might also be the solution

[poisondeathray]

why are you re-encoding dv to dv ?

might be a bug in mencoder or that build; either works ok in ffmpeg (copying a stream section, or re-encoding to ntsc-dv)

[reising1]

Thank you for the feedback. I ended up using this command. What do you think? I am forcing dvsd because the previous avi files that I clipped with the simpler version of this command produced dvsd files, and I want all my clips to be consisitent in case I do any further processing.

mencoder -ss 0 -endpos 35 Movie.avi -oac pcm -ovc lavc -lavcopts vcodec=dvvideo:vbitrate=28771224:format=411P -ffourcc dvsd -o works.avi

[poisondeathray]

Re-encoding with DV is a lossy conversion process (you lose quality each time as the video is decompressed and recompressed) ; but steam copying preserves quality - was there a reason why you were re-encoding instead of stream copying?

[reising1]

Using -ovc copy did not cause the clip to be created properly. For example, on Mac, in Finder, when I clicked on the avi file, it preview was a black screen (as opposed to the first frame of the video)

[poisondeathray]

Do you mean the re-encoding the audio or the video?

The video , DV is being re-encoded to DV (not stream copied). So this incurs a generation loss.

In your case, the audio doesn't matter, because it's uncompressed PCM => uncompressed PCM . This is a lossless transformation (you're not using lossy audio compression)

Using -ovc copy did not cause the clip to be created properly. For example, on Mac, in Finder, when I clicked on the avi file, it preview was a black screen (as opposed to the first frame of the video)

might be a bug in mencoder (or that specific binary), or your specific file then. DV is pretty ubiquitious and intraframe (you can make cuts with frame accuracy without any problems)

[Selur]

about the preview on video copy: did you compare the results using mediainfo like I suggested?