Hello, I use mpeg2enc and mplex to create my DVD from videos made with Cinelerra. Cinelerra outputs an YUV4MPEG stream which I encode "on the fly" with mpeg2enc. Here's the pipe I use : /usr/bin/yuvcorrect -T INTERLACED_BOTTOM_FIRST | /usr/bin/yuvscaler -v 0 -I ACTIVE_702x560+8+8 -M BICUBIC | /usr/bin/mpeg2enc -v 0 -r 32 -4 1 -2 1 -V 1853 -s -D 1 0 -g 6 -G 15 -I 1 -b 9800 -D 10 -f 8 -o $1
I also output an AC3 audio stream, and I use mplex to create the mpeg video: mplex -f 8 -b 1835 -r 10404 audio.ac3 video.m2v -o movie.mpeg However, I noticed a strange thing in mplex output : INFO: [mplex] Video Stream length: 505039125 bytes INFO: [mplex] Sequence headers: 727 INFO: [mplex] Sequence ends : 1 INFO: [mplex] No. Pictures : 10904 INFO: [mplex] No. Groups : 727 INFO: [mplex] No. I Frames : 727 avg. size 58042 bytes INFO: [mplex] No. P Frames : 10177 avg. size 45479 bytes INFO: [mplex] No. B Frames : 0 avg. size 0 bytes There seems to be no B frame at all in the mpeg. That's strange since it's written in the mpeg2enc manpage : Note: Mpeg2enc is currently hard-wired to produce 2 B frames between each I/P frame unless the GOP size forces less. This is reasonable for medium to high bitrates (>= 1Mbps) but probably sub-optimal for low-bitrate encoding. I recognize I did not use the following option in my mpeg2enc pipe command : -P|--force-b-b-p This flag forces the GOP size selection to choose sizes that ensure 2 B frames appear between adjacent I/P frames. Several common MPEG-1 decoders can't handle streams where less than 2 B-frames appear between I/P frames. But I assumed I don't have to use that option in order to get 2 B frames in each GOP. What's wrong? Did I use a wrong setting? I really would like to get 2 B frames in each GOP, to get the best image quality (as you probably noticed, I encode in CBR at 9800 kbps). Thank you for your help. Nicolas, Paris. ------------------------------------------------------- This SF.Net email is sponsored by xPML, a groundbreaking scripting language that extends applications into web and mobile media. Attend the live webcast and join the prime developer group breaking into this new coding territory! http://sel.as-us.falkag.net/sel?cmd=lnk&kid=110944&bid=241720&dat=121642 _______________________________________________ Mjpeg-users mailing list Mjpeg-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/mjpeg-users
