Hallo > Based on the values I used to encode the mpeg2 files I've been > testing with "dvdview", it seems that the reported value of bitrate > is always 2.5 times the value I encoded at. So if I set the > max bitrate at 10000, the reported value is 25000. Which means, > I can easily figure out the actual value, but I'm still very > curious as to why the number is multiplied. Usually the bitrate reported by a mpegplayer is the maximal bitrate. Set somewere in the header.
> But I'm more curious about why the number never changes (so now this > is an mjpegtools question). I generally run "mpeg2enc" something > like: > % mpeg2enc -S 400 -B 384 -q 4 -b 8000 -f 8 -r 16 -N -I 1 -v 0 -o > iyis_vid.m2v < iyis_vid_dn.yuv > > So, why if I'm doing variable bitrate encoding, does the bitrate > never change? > > NOTE: these were from encodings done with version 1.6.1 of mjpegtools. > > Another question that occured to me concerns the -B option: in > the above senario, would the video stream I'm encoding use up > to 8000kbs, or would it actually just use (8000-384)kbps? So, > if I were to set the max bitrate at 10000, would using the -B > option preserve space for other streams? Or do I also need to No, it does not preserve anything. > make sure to subtract other stream usage from the 10000 to > stay within the DVD spec? Take a look at the manpage of mepg2enc (-S -B option). Usually you combine the -B with the -S option. If you use the -f 8 (DVD Profile) the -B option alone does not make really sense because the -S (filesize) is set to indefinite. The -B option makes only sense when you multiplex the streams and want a certain final filesize. Else the -b (bitrate) is the more important option it defines how much bitrate is used for the video. And than you add the audio. > And, I'd also like to know what some of the other values reported > with each SequenceHeader are: > VBV buf.size -- generally reported as 112, except from > an mpeg-1 trailer I downloaded, which reported 3. > aspect code -- always seems to be 2 for mpeg2enc output > (including an SVCD), and 1 for an mpeg-1 file > I have. > constrained -- no idea. It was always false except the > mpeg-1 trailer. > profile -- don't know, but possible values are: Simple, > Main, SNR, Spatial and High. > level -- don't know, but possible values are: Low, Main, > High and High1440. I guess that the aspect code is directly compareabel with the mpeg2enc -a display aspect ratio codes. And 2 would mean 4:3. The level/profile option look like it has something to do with HD-TV. I have no idea about the other values. auf hoffentlich bald, Berni the Chaos of Woodquarter Email: [EMAIL PROTECTED] [EMAIL PROTECTED] www: http://www.lysator.liu.se/~gz/bernhard ------------------------------------------------------- This sf.net email is sponsored by:ThinkGeek Welcome to geek heaven. http://thinkgeek.com/sf _______________________________________________ Mjpeg-users mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/mjpeg-users
