[Flac-dev] are 588 sample frames subset or nonsubset?

[Howard Farrar]

Hi Josh

I realise that the compression ratio is related to the signal stationarity
and blocksize, but the tests I have performed seemed to indicate that using
a blocksize of 588 samples only looses about 1% of compression ratio against
a blocksize of 1152 or 4608 samples.

Encoding with a blocksize of 588 samples would have benefits for the rest of
my system.

Howard

-----Original Message-----
From: Josh Coalson [mailto:xflac at yahoo.com] 
Sent: 23 May 2008 21:03
To: howard.farrar at meridian.co.uk; flac-dev at xiph.org
Subject: Re: [Flac-dev] are 588 sample frames subset or nonsubset?

hi Howard, I'll check into the discrepancy but having the FLAC
blocksize match the CD sample frame size is probably not desirable.
the optimal blocksize for FLAC is relative to the stationarity of
the signal and the 588 sample frame is not related to that, it's
an artifact of optimal storage on CD.

Josh

--- Howard Farrar <howard.farrar at meridian.co.uk> wrote:

> Hi
> 
> I am thinking of ripping albums to a single flac file with embedded
> cuesheet.  As track and index points have to be on a 588 sample
> boundary due
> to the CD TOC standard working in 588 sample frames, I thought it may
> be beneficial to rip CDs with a blocksize of 588 samples.
> 
> According to the format page on sourcefourge a stream is subset if
> 
> 	"The blocksize bits in the frame header must be 0001-1110.
> 	 The blocksize must be <=16384;
> 	 if the sample rate is <= 48000Hz, the blocksize must be <=4608.
> 
> As far as I can tell, this means that a blocksize of 588 should be
> subset,
> although the blocksize would be a 16 bit value at the end of the
> frame
> header.
> 
> However when I try encoding with flac 1.2.1 it says that only the
> blocksizes
> that can be represented in the 4 bits in the early part of the frame
> header.
> 
> Which is correct?  Can anyone forsee any problems with encoding with
> a block
> size of 588 samples?
> 
> Best Regards
> 
> Howard
> 
> 
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