--- Erik de Castro Lopo <[EMAIL PROTECTED]> wrote: > HI all, > > I have already added FLAC support to libsndfile and I am now > working on adding support for OggFLAC.
cool. > I have a couple of > question about things that seem radically different between > regular FLAC and OggFLAC. > > 1) FLAC has a function: > > FLAC__seekable_stream_decoder_get_decode_position > > but there seems to be no corresponding function: > > OggFLAC__seekable_stream_decoder_get_decode_position > > Why is that? that function is not really possible with ogg flac because flac frames (which are in ogg packets) can be broken up into multiple pages. the reason I added that function was because of a design flaw in native FLAC, where raw frames cannot be fully extracted without decoding. for example, for taking an existing native FLAC file, extracting the frames and putting them in a matroska container, the program that does this has to decode a frame, use that function to find where it is, and know that the bytes between it and the previous call is where the frame is. but with ogg flac that can span a page boundary so you can't extract the frame that way. best to use an ogg decoder to recover pages, then packets. then you don't even need to decode the flac frames. unless there is another reason you need that kind of functionality? (p.s. this might also help: http://flac.sourceforge.net/ogg_mapping.html) > 2) I have registered a metadata callback function with > OggFLAC__seekable_stream_decoder_set_metadata_callback and > I'm looking at the metadata struct being passed back. When > using regular FLAC the field: > > metadata->data.stream_info.total_samples > > is set correctly, but with OggFLAC it seems to always be > zero. Why? > > Can anyone shed any light? normally the flac encoder goes back to fill in missing STREAMINFO fields after encoding is finished. the encoder may not know total_samples when encoding starts; if not it has to go back and put it in at the end of encoding. even when encoding to ogg flac as of flac-1.1.2 it should do that. so either: - the ogg flac file was encoded with flac-1.1.1 or earlier - the ogg flac file was encoded to stdout so the writeback couldn't happen (flac --ogg file.wav > file.flac) - there is a bug somewhere! Josh __________________________________ Yahoo! Mail - PC Magazine Editors' Choice 2005 http://mail.yahoo.com _______________________________________________ Flac-dev mailing list Flac-dev@xiph.org http://lists.xiph.org/mailman/listinfo/flac-dev
