[Flac-dev] slow FLAC__file_decoder_seek_absolute()...

[Brendan Dowling]

On Fri, Jan 25, 2002 at 07:22:05PM -0800, Josh Coalson wrote:
> 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.
> 

Thanks Josh.  I tested the player with some files encoded by another 
guy here at work, and seeking into the files seems to work perfectly.  
So the Phatbox now plays FLAC files.  Although, it's not yet in the
standard firmware download from the web page, and encoding is not yet
included in the capabilities of the Phatnoise Music Manager software.
(Although I hope to get the Windows software guys to include the ability
to at least include .flac files in playlists soon and adding the player
to the standard firmware distribution should be easy).  

So, thanks again.  And maybe if I become more acquainted with the
libFLAC code, I'll be able to help with improving searching in
seektable-less and max_framesize-less files.  


Brendan Dowling
Embedded Systems Engineer
Phatnoise, Inc.
http://www.phatnoise.com





> 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 at 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 at 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 at phatnoise.com
> > > Phatnoise, Inc.
> > > http://www.phatnoise.com/
> 
> 
> 
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