[Flac-dev] Re: Reg. FLAC decoding

[Josh Coalson]

--- Joe Steeve [EMAIL PROTECTED] wrote:
 Is it possible for the frame-header.bits_per_sample,
 frame-header.sample_rate to differ from frame to frame??

no, not in file storage.  that would be invalid.  but you should
guard against it anyway, e.g. aborting playback if it changes.

Josh





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[Flac-dev] Re: Reg. FLAC decoding

[Joe Steeve]

Sorry for the delay in getting back to you., I was working on something
else and just now got FLAC to work.

Ok., FLAC files are playing now :) Cheers. There is a slight noise
happening in the background., which i'm figuring out. I hope that it'll
be solved soon. However, i wanted to know if there are any ARM specific
optimizations that can be done. The processor is a 166MHz processor. Do
you think it is ok?

-- 
Joe Steeve (http://www.joesteeve.org/)
Z500 Development team (http://www.z500series.com/)

Terminus Graphics Studios
http://www.terminus.in/

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[Flac-dev] Re: Reg. FLAC decoding

[Josh Coalson]

--- Joe Steeve [EMAIL PROTECTED] wrote:

 Sorry for the delay in getting back to you., I was working on
 something
 else and just now got FLAC to work.
 
 Ok., FLAC files are playing now :) Cheers. There is a slight noise
 happening in the background., which i'm figuring out. I hope that
 it'll
 be solved soon. However, i wanted to know if there are any ARM
 specific
 optimizations that can be done. The processor is a 166MHz processor.
 Do
 you think it is ok?

we don't have any ARM optimizations yet, just x86 and ppc. but
yes, FLAC__lpc_restore_signal() will give the most bang for the
buck and is the easiest (it's just a multiply-accumulate-shift
loop).

unsigned i, j;
FLAC__int32 sum;
for(i = 0; i  data_len; i++) {
sum = 0;
for(j = 0; j  order; j++)
sum += qlp_coeff[j] * data[i-j-1];
data[i] = residual[i] + (sum  lp_quantization);
}

the next would probably be FLAC__fixed_restore_signal(), which
is also easy, and FLAC__bitbuffer_read_rice_signed_block(),
which is unfortunately complicated.

Josh





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[Flac-dev] Re: Reg. FLAC decoding

[Joe Steeve]

On Fri, 2005-09-30 at 23:14, Josh Coalson wrote:
 but all samples in buffer[] are 32-bit signed integers in host
 order, regardless of the bits-per-sample of the frame.  so to get
 them down to shorts (assuming they'll fit), do like:
 
   FLAC__int32 * LChannel = buffer[0];
   short TempSource = (short)LChannel[LPos];
 
 instead of
 
   LChannel = (unsigned char *)buffer[0];
   short * TempSource = (short *)LChannel[LPos];

 let me know if this works or if you have other questions.

I tried this., but still i dont get the proper output. I'm still
debugging with the decoder. I'll get back when I get doubts.

-- 
Joe Steeve (http://www.joesteeve.org/)
Z500 Development team (http://www.z500series.com/)

Terminus Graphics Studios
http://www.terminus.in/

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[Flac-dev] Re: Reg. FLAC decoding

[Josh Coalson]

--- Joe Steeve [EMAIL PROTECTED] wrote:
 On Fri, 2005-09-30 at 23:14, Josh Coalson wrote:
  but all samples in buffer[] are 32-bit signed integers in host
  order, regardless of the bits-per-sample of the frame.  so to get
  them down to shorts (assuming they'll fit), do like:
  
FLAC__int32 * LChannel = buffer[0];
short TempSource = (short)LChannel[LPos];
  
  instead of
  
LChannel = (unsigned char *)buffer[0];
short * TempSource = (short *)LChannel[LPos];
 
  let me know if this works or if you have other questions.
 
 I tried this., but still i dont get the proper output. I'm still
 debugging with the decoder. I'll get back when I get doubts.

one thing that can help: create a stereo WAVE file with one
sample in each channel with a specific bit pattern like
0x55aa 0x5aa5, compress to FLAC, and decode that.  then it is
easy in a debugger to see how the samples are stored.

Josh




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