Hi, I have posted this three times to the flac-dev, vorbis-dev, and ogg-dev mailing lists. I wanted to see what code there was currently to support Ambisonics. So I downloaded the code from the xiph download page for libogg-1.1.3, libvorbis-1.1.2, vorbis-tools-1.1.1 and flac-1.1.4, but wasn't able to find anything. If it exists then I missed it, so could somebody please point me to it. Many thanks, Martin -- Martin J Leese E-mail: martin.leese@stanfordalumni.org Web: http://members.tripod.com/martin_leese/
Martin, I do not believe that there is any need for code specifically supporting Ambisonics. FLAC supports conversion to and from other audio formats which hold multiple channels. Ambisonics B-format involves channels WXYZ, C-format is UHJ or BHJ, G-Format can be any number of channels, but typically 5.1 on DVD. You can work with Ambisonic recordings by either using individual mono files for each of the Ambisonic channels, or by using a 4-channel or 6-channel AIFF. All of these files can be compressed into FLAC and expanded again without loss. While FLAC does some special treatment of 2-channel files to detect correlation, this should not interfere with Ambisonic content. Ambisonics has much in common with mid-side encoding of dimensional recordings, and FLAC with automatically detect the most efficient compression based on any correlation. For this reason, you might find smaller files with multiple stereo pairs (e.g. WX & YZ) instead of multiple mono files or a massive 4-channel file. But to return to your question, exactly what kind of "support" are you looking for? Where is your Ambisonic material coming from? What format are the files? By format, I am asking primarily what the file format is (RIFF/WAV, AIFF, other), but also which Ambisonic "format" among B-format, C-format, or G-format. Brian Willoughby Sound Consulting On Mar 22, 2007, at 14:12, Martin Leese wrote: Hi, I have posted this three times to the flac-dev, vorbis-dev, and ogg-dev mailing lists. I wanted to see what code there was currently to support Ambisonics. So I downloaded the code from the xiph download page for libogg-1.1.3, libvorbis-1.1.2, vorbis-tools-1.1.1 and flac-1.1.4, but wasn't able to find anything. If it exists then I missed it, so could somebody please point me to it. Many thanks, Martin -- Martin J Leese E-mail: martin.leese@stanfordalumni.org Web: http://members.tripod.com/martin_leese/
FLAC has no special support for ambisonics. --- Martin Leese <martin.leese@stanfordalumni.org> wrote:> Hi, > > I have posted this three times to the flac-dev, > vorbis-dev, and ogg-dev mailing lists. > > I wanted to see what code there was currently > to support Ambisonics. So I downloaded the > code from the xiph download page for > libogg-1.1.3, libvorbis-1.1.2, vorbis-tools-1.1.1 > and flac-1.1.4, but wasn't able to find anything. > > If it exists then I missed it, so could somebody > please point me to it. > > Many thanks, > Martin > -- > Martin J Leese > E-mail: martin.leese@stanfordalumni.org > Web: http://members.tripod.com/martin_leese/____________________________________________________________________________________ Finding fabulous fares is fun. Let Yahoo! FareChase search your favorite travel sites to find flight and hotel bargains. http://farechase.yahoo.com/promo-generic-14795097
On 3/22/07, Brian Willoughby <brianw@sounds.wa.com> wrote: ...> But to return to your question, exactly what kind of "support" are > you looking for?I wasn't looking for any particular support, but just to see what support was there (if any). ...> I do not believe that there is any need for code specifically > supporting Ambisonics. FLAC supports conversion to and from other > audio formats which hold multiple channels. Ambisonics B-format > involves channels WXYZ, C-format is UHJ or BHJ, G-Format can be any > number of channels, but typically 5.1 on DVD. You can work with > Ambisonic recordings by either using individual mono files for each > of the Ambisonic channels, or by using a 4-channel or 6-channel > AIFF. All of these files can be compressed into FLAC and expanded > again without loss.B-Format is not a set of speaker feeds, and needs to be routed to a decoder in your living room. It would therefore be useful to have a flag identifying the file as B-Format. For example, the ".amb" format (based on WAVE-EX) uses unique GUIDs for this. UHJ format is stereo compatible, but can also be decoded back into surround sound. Again, a flag identifying the file as UHJ would be useful to give a player the opportunity to do this. The ".uhj" format (based on WAVE and WAVE-EX) uses a chunk for this. G-Format files can contain coefficients to allow the B-Format channels to be recovered. These can then be decoded to a speaker layout different from the one assumed when the G-Format file was created. This can only happen if there is some way of identifying the file as G-Format, and some way of incorporating the coefficients into it. In each case there is no need to change the audio data, but in each case there is a need for identifying flags. Hope this helps. Regards, Martin -- Martin J Leese E-mail: martin.leese@stanfordalumni.org Web: http://members.tripod.com/martin_leese/