When I encode a monophonic wav file, I would expect the resulting ogg file to be at about half the bit rate specified on the command line, as stated in the "oggenc -h" help text: "The 6 modes are approximately 112, 128, 160, 192, 256, and 350 kbps (for stereo 44.1kHz input. Halve these numbers for mono input).". This doesn't seem to be happening, though. I took a 16-bit, 44.1 khz mono wav file, 2:38 long (about 12MB in size -- an old pop song), and encoded it with "oggenc -b 160 file.wav". Oggenc reported an average bit rate of 150k-plus. The resulting ogg file is about 2.7 MB. When I play it in Winamp, the on-screen display shows that it is mono, and the bit rate varies in the range of roughly 140-170k. From the help text, and my experience with MP3 encoders, I expected to see bit rates of about 70-90k, and a file size of under 2 MB. Unless I'm simply misunderstanding what appears to be reasonably plain English, it would appear that the help text and the actual behavior of the code are out of sync. Other than this fairly minor point, so far b4 is doing very nicely. Craig _________________________________________________________ Do You Yahoo!? Get your free @yahoo.com address at http://mail.yahoo.com --- >8 ---- List archives: http://www.xiph.org/archives/ Ogg project homepage: http://www.xiph.org/ogg/ To unsubscribe from this list, send a message to 'vorbis-request@xiph.org' containing only the word 'unsubscribe' in the body. No subject is needed. Unsubscribe messages sent to the list will be ignored/filtered.
Craig Dickson wrote:> When I encode a monophonic wav file, I would expect the resulting ogg file > to be at about half the bit rate specified on the command line, as stated in > the "oggenc -h" help text: "The 6 modes are approximately 112, 128, 160, > 192, 256, and 350 kbps (for stereo 44.1kHz input. Halve these numbers for > mono input).".The last sentence means that you should halve those numbers yourself, because these values are the 6 modes for stereo input. I tried it on a mono file with 'oggenc -b 80 input.wav' and it worked fine - i got a mono .ogg with an ABR of 83kbit/s out of that. This really is confusing, and I have no idea without consulting my pocket calculator what bitrates I should choose when actually having an multichannel input file. I think it might be a good idea to give oggenc, in addition to the -b option, an option '-m' (for 'mode', just as an example and it's still unused, btw) followed by a number between 1 and 6 and then let oggenc choose the appropriate bitrate for the input file. (Would make it very useful when batch-encoding .wavs with varying amounts of channels at the same quality level (that is what most users want, I guess).) A nice side-effect would be the transparent encoding of non-44.1kHz waves ... getting ~70kbit/s when using -b 112 is somewhat irritating. What I would not want is to replace the -b option. Being able to set the bitrate directly surely is useful from time to time. Assuming, the option '-m 2' (which should be default then, because -b 128 is default) gives a stereo_input.wav around 128kbit/s, it should give a mono_input.wav 64kbit/s, a 3channel_input.wav 192kbit/s, etc. Then, there's something else I don't understand. Quoting http://www.xiph.org/ogg/vorbis/: "[...] for high quality (44.1-48.0kHz, 16+ bit, polyphonic) audio and music at fixed and variable bitrates from 16 to 128 kbps/channel." How come? oggenc doesn't support 32kbit/s for stereo files right now (?), but I guess this still hast to be implemented anyways ... but on the other hand oggenc seems to support 350kbit/s for stereo files, which is 175kbit/s per channel and not 128kbit/s. Or is 350kbit/s intended only for 3channel-input with 117kbit/s per channel? It'd be great if someone could make things more clear for the 1.0 release ... Bye, Moritz --- >8 ---- List archives: http://www.xiph.org/archives/ Ogg project homepage: http://www.xiph.org/ogg/ To unsubscribe from this list, send a message to 'vorbis-request@xiph.org' containing only the word 'unsubscribe' in the body. No subject is needed. Unsubscribe messages sent to the list will be ignored/filtered.
On Mon, Feb 26, 2001 at 05:01:10PM -0800, Craig Dickson wrote:> When I encode a monophonic wav file, I would expect the resulting ogg file > to be at about half the bit rate specified on the command line, as stated in > the "oggenc -h" help text: "The 6 modes are approximately 112, 128, 160, > 192, 256, and 350 kbps (for stereo 44.1kHz input. Halve these numbers for > mono input).". > > This doesn't seem to be happening, though. I took a 16-bit, 44.1 khz mono > wav file, 2:38 long (about 12MB in size -- an old pop song), and encoded it > with "oggenc -b 160 file.wav". Oggenc reported an average bit rate of > 150k-plus.The text is correct but mildly ambiguous. What it means to say is "the encoder does what you tell it to". If you encode a mono wav with -b 160 it gives you a roughly 160 kbps file (kbps is a measure of size, not quality). A 160kbps file in stereo is 80kbps mono for the same quality (as things stand right now). What you wanted to do was use -b 80. --- >8 ---- List archives: http://www.xiph.org/archives/ Ogg project homepage: http://www.xiph.org/ogg/ To unsubscribe from this list, send a message to 'vorbis-request@xiph.org' containing only the word 'unsubscribe' in the body. No subject is needed. Unsubscribe messages sent to the list will be ignored/filtered.