[Flac-dev] wav to flac corruption

[Stuart Fisher]

As a player writer this doesn't really surprise me very much. My guess is 
that many players have hard-coded 16-bit code paths. Mine certainly does, 
although in my defence it is a mobile phone FLAC player and I wouldn't 
really expect anybody to put broadcast quality audio on a mobile phone. 
Something to look at for future development though!

Stuart ("OggPlay project")


----- Original Message ----- 
From: "Justin Waddell" <jwaddell at gmail.com>
To: "Brian Willoughby" <brianw at sounds.wa.com>
Cc: <flac-dev at xiph.org>
Sent: Friday, February 08, 2008 12:55 AM
Subject: Re: [Flac-dev] wav to flac corruption


>I have exactly the same problem.
>
> I encoded a BWF file to flac and then then decoded back to wav, using
> --keep-foreign-metadata, and I ended up with a bit-perfect copy of the
> original BWF. So I was fairly confident that the flac encoding is
> working correctly, the problem definitely appears to be with the flac
> players.
>
> Unfortunately it seems that the majority of flac players cannot play
> 24bit files - winamp, windows media player (with flac plugin), vlc,
> amarok, kaffeine and a few others ALL failed to play the file. I would
> either get silence, static, or a complete refusal to play the file.
> The only player that played it successfully was Foobar 2000 on
> Windows.
>
> More seriously from my point of view is the Java flac plugin also
> fails, which has major repercussions for the project I work on (the
> National Archives of Australia Xena project -
> http://xena.sourceforge.net).
>
> I don't know how much the flac developers have to do with the player
> implementations, but this does seem to be a major problem across
> almost the full board of flac players.
>
> J.
>
> On Feb 7, 2008 9:59 AM, Brian Willoughby <brianw at sounds.wa.com> wrote:
>> I have one theory about your playback problem: Many flac solutions
>> load the entire flac and decompress the samples before passing them
>> on to the player.  In your case, the conversion code may be running
>> out of memory on 24-bit files where it does not run out of memory on
>> 16-bit files of the same duration.  Another possibility is that the
>> flac player does not support 24-bit data properly.
>>
>> As Erik mentioned, conversion to 16-bit is a loss of quality.  Even
>> if you are willing to do this, you should have a very good dithering
>> algorithm to avoid quantization noise.
>>
>> The problem you are having is not with flac.  Your problem is with
>> your player.  The encode and decoder both support 24-bit files all
>> the way up to the 4 GB limit.  I have made several 24-bit multitrack
>> recordings, and flac always handles these files without loss of
>> data.  The flac players I have fully support long 24-bit files.  It
>> seems that you need to replace your player if it cannot handle large
>> 24-bit files.
>>
>> You don't want to reduce the quality of your source or abandon
>> lossless coding just because the players are buggy!
>>
>> Brian Willoughby
>> Sound Consulting
>>
>>
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