Brendan Dowling
2004-Sep-10 16:45 UTC
[Flac-dev] slow FLAC__file_decoder_seek_absolute()...
Hi,
I checked the archives, but I didn't find anything regarding this
problem. FLAC__file_decoder_seek_absolute takes an incredibly long time
to seek. What can I do about this? How do I fix it?
Here's how I'm calling the function:
if (argc > 2) {
secs = atoi(argv[2]);
seek_point = (FLAC__uint64) secs * sample_rate;
printf("seeking to %d:%02d\n", secs/60, secs%60);
flac_status = FLAC__file_decoder_seek_absolute(decoder, seek_point);
if (flac_status) printf("seek absolute = %d\n", flac_status);
}
FLAC__file_decoder_process_remaining_frames(decoder);
Thanks,
Brendan Dowling
p.s., I am making a simple FLAC file player that runs on the Phatnoise
Car Audio System (see http://www.phatnoise.com/ for more info).
---
Brendan Dowling
crypt@phatnoise.com
Phatnoise, Inc.
http://www.phatnoise.com/
Brendan Dowling
2004-Sep-10 16:45 UTC
[Flac-dev] slow FLAC__file_decoder_seek_absolute()...
I have a new idea for speeding up seeking. Would it help if I were to decode a few frames (and throw away the decoded data) before doing the FLAC__file_decoder_seek_absolute() call? This would be so that the decoder object could prime its min_framesize and max_framesize variables. Brendan Dowling Embedded Systems Engineer Phatnoise, Inc. On Thu, Jan 17, 2002 at 05:46:00PM -0800, Brendan Dowling wrote:> Hi, > > I checked the archives, but I didn't find anything regarding this > problem. FLAC__file_decoder_seek_absolute takes an incredibly long time > to seek. What can I do about this? How do I fix it? > > Here's how I'm calling the function: > > > if (argc > 2) { > secs = atoi(argv[2]); > seek_point = (FLAC__uint64) secs * sample_rate; > printf("seeking to %d:%02d\n", secs/60, secs%60); > > flac_status = FLAC__file_decoder_seek_absolute(decoder, seek_point); > > if (flac_status) printf("seek absolute = %d\n", flac_status); > } > > FLAC__file_decoder_process_remaining_frames(decoder); > > > > Thanks, > > Brendan Dowling > > > p.s., I am making a simple FLAC file player that runs on the Phatnoise > Car Audio System (see http://www.phatnoise.com/ for more info). > > --- > Brendan Dowling > crypt@phatnoise.com > Phatnoise, Inc. > http://www.phatnoise.com/ > > > > > _______________________________________________ > Flac-dev mailing list > Flac-dev@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/flac-dev
Brendan Dowling
2004-Sep-10 16:45 UTC
[Flac-dev] slow FLAC__file_decoder_seek_absolute()...
I think I figured out where the problem is. In my metadata_callback, I added a thing to print out the max_framesize and max_framesize from the stream_info block. Those are both zero. The ..._seek_absolute() function of the SeekableStreamDecoder uses the max_framesize to guess at where to seek. It doesn't seem to handle the case when max_frame_size is zero very well. I'm looking at seekable_stream_decoder.c, by the way. The files I am playing were encoded using the command line 'flac' encoder and default options. Brendan Dowling Phatnoise, Inc. crypt@phatnoise.com http://www.phatnoise.com/ On Thu, Jan 17, 2002 at 05:46:00PM -0800, Brendan Dowling wrote:> Hi, > > I checked the archives, but I didn't find anything regarding this > problem. FLAC__file_decoder_seek_absolute takes an incredibly long time > to seek. What can I do about this? How do I fix it? > > Here's how I'm calling the function: > > > if (argc > 2) { > secs = atoi(argv[2]); > seek_point = (FLAC__uint64) secs * sample_rate; > printf("seeking to %d:%02d\n", secs/60, secs%60); > > flac_status = FLAC__file_decoder_seek_absolute(decoder, seek_point); > > if (flac_status) printf("seek absolute = %d\n", flac_status); > } > > FLAC__file_decoder_process_remaining_frames(decoder); > > > > Thanks, > > Brendan Dowling > > > p.s., I am making a simple FLAC file player that runs on the Phatnoise > Car Audio System (see http://www.phatnoise.com/ for more info). > > --- > Brendan Dowling > crypt@phatnoise.com > Phatnoise, Inc. > http://www.phatnoise.com/ > > > > > _______________________________________________ > Flac-dev mailing list > Flac-dev@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/flac-dev
sorry about the delay... first, yes you are calling it correctly. if your encoded files have max_framesize == 0, then that should mean that either 1) you were using the command-line flac to encode to stdout; or 2) you are using libFLAC directly. if 2, you can replicate the functionality that is in src/flac/encode.c:metadata_callback() to write back statistics and seek table to the metadata in the flac file because currently this is not done automatically by the library. (eventually I will fix this the right way.) that will speed up seeks on the file. second, even without the seek table or knowing max_framesize, the seek routine does adjust the approximate_bytes_per_frame as it decodes target frames. so I don't think it would help too much compute the framesizes of the first few frames because the seek current implementation in this case is only really weak when the bitrate varies widely in the stream. in that case knowing the first few frame sizes doesn't really help much. on my todo list is a true binary search which should improve things for streams with no seektable and wide bitrate swings. Josh P.S. be sure to keep us posted about PhatBox! --- Brendan Dowling <crypt@phatnoise.com> wrote:> I think I figured out where the problem is. In my metadata_callback, > > I added a thing to print out the max_framesize and max_framesize from > the stream_info block. Those are both zero. The ..._seek_absolute() > > function of the SeekableStreamDecoder uses the max_framesize to guess > at where to seek. It doesn't seem to handle the case when > max_frame_size is zero very well. I'm looking at > seekable_stream_decoder.c, by the way. > > > The files I am playing were encoded using the command line 'flac' > encoder and default options. > > > Brendan Dowling > Phatnoise, Inc. > crypt@phatnoise.com > http://www.phatnoise.com/ > > > > > On Thu, Jan 17, 2002 at 05:46:00PM -0800, Brendan Dowling wrote: > > Hi, > > > > I checked the archives, but I didn't find anything regarding this > > problem. FLAC__file_decoder_seek_absolute takes an incredibly long > time > > to seek. What can I do about this? How do I fix it? > > > > Here's how I'm calling the function: > > > > > > if (argc > 2) { > > secs = atoi(argv[2]); > > seek_point = (FLAC__uint64) secs * sample_rate; > > printf("seeking to %d:%02d\n", secs/60, secs%60); > > > > flac_status = FLAC__file_decoder_seek_absolute(decoder, > seek_point); > > > > if (flac_status) printf("seek absolute = %d\n", flac_status); > > } > > > > FLAC__file_decoder_process_remaining_frames(decoder); > > > > > > > > Thanks, > > > > Brendan Dowling > > > > > > p.s., I am making a simple FLAC file player that runs on the > Phatnoise > > Car Audio System (see http://www.phatnoise.com/ for more info). > > > > --- > > Brendan Dowling > > crypt@phatnoise.com > > Phatnoise, Inc. > > http://www.phatnoise.com/__________________________________________________ Do You Yahoo!? Great stuff seeking new owners in Yahoo! Auctions! http://auctions.yahoo.com