Hi, Am 15.11.2010 14:03, schrieb [email protected]:
As an example, this is what I get when I transcode AVCHD to mjpeg with ffmpeg :$ ffmpeg -i 20100520101256.m2ts -an -vcodec mjpeg -b 24000k render.mov FFmpeg version SVN-r25679, Copyright (c) 2000-2010 the FFmpeg developers built on Nov 5 2010 09:22:10 with gcc 4.5.1 [... snip ...] Input #0, mpegts, from '20100520101256.m2ts': Duration: 00:00:11.46, start: 1.000033, bitrate: 21952 kb/s Program 1 Stream #0.0[0x1011]: Video: h264, yuv420p, 1920x1080 [PAR 1:1 DAR 16:9], 50 fps, 50 tbr, 90k tbn, 50 tbc Stream #0.1[0x1100]: Audio: ac3, 48000 Hz, 5.1, s16, 448 kb/s Stream #0.2[0x1200]: Subtitle: pgssub [buffer @ 0xc53920] w:1920 h:1080 pixfmt:yuv420p [ffsink @ 0xc1a010] auto-inserting filter 'auto-inserted scaler 0' between the filter 'src' and the filter 'out' [scale @ 0xc1ddf0] w:1920 h:1080 fmt:yuv420p -> w:1920 h:1080 fmt:yuvj420p flags:0x4 Output #0, mov, to 'render.mov': Metadata: encoder : Lavf52.84.0 Stream #0.0: Video: mjpeg, yuvj420p, 1920x1080 [PAR 1:1 DAR 16:9], q=2-31, 24000 kb/s, 50 tbn, 50 tbc Stream mapping: Stream #0.0 -> #0.0 [... snip ...] In this case, there's a colorspace conversion from 'yuv420p' to 'yuvj420p', but is it really "lossy" in itself since colorspace "family" and chroma subsampling are the same (YCbCr and 4:2:0 respectively) ?
yuv420p has video range for luma and chroma. yuvj420p has full range (0..255). So the conversion simply maps the video range values to full range (e.g. with a loopup table).
Furthermore, am I right to think that colorspace conversion can be avoided in cinelerra by choosing "YUV-8 Bit" or "YUVA-8 Bit" as Color model in the project parameters, when working with 8-bits YCbCr footage ?
You save the conversion to RGB if you use these. But these colormodels are 4:4:4, so you'll upsample the chroma planes, which doubles the memory footprint of the video frames compared to 4:2:0. Burkhard _______________________________________________ Cinelerra mailing list [email protected] https://init.linpro.no/mailman/skolelinux.no/listinfo/cinelerra
