[Flac-dev] Legal sample rates

[Josh Coalson]

--- Erik de Castro Lopo <erikd-flac at mega-nerd.com> wrote:
> Hi all,
> 
> I'm trying to use the FLAC C libraries to encode audio.
> 
> I'm doing something like:
> 
>   FLAC__seekable_stream_encoder_set_channels(pflac->fse, 1);
>   FLAC__seekable_stream_encoder_set_sample_rate(pflac->fse, 11025);
>   FLAC__seekable_stream_encoder_set_bits_per_sample(pflac->fse, 8);
> 
>   if ((bps = FLAC__seekable_stream_encoder_init(pflac->fse)) !=
> FLAC__SEEKABLE_STREAM_DECODER_OK)
>   {	printf ("Error : FLAC encoder init returned error : %s\n",
>                 FLAC__SeekableStreamEncoderStateString [bps]);
>         exit (1);
> 	}
> 
> and I'm triggering the error message, but the most information I
> can get from the FLAC__SeekableStreamEncoderStateString method is
> FLAC__SEEKABLE_STREAM_ENCODER_STREAM_ENCODER_ERROR.
> 
> SOmeone else has dug through the FLAC libraries and came to the 
> conclusion that FLAC doesn't accept the given sample rate (11025).
> I therefore tried to test the error return value of the
> set_sample_rate()
> method, but found that it always returns TRUE (ie no error).
> 
> Is there someway of figuring out if a sample rate is valid?

that's the right way.

the reason it's being rejected is the encoder is configured to
obey the subset:

http://flac.sourceforge.net/format.html#subset

to encode 11.025 kHz you need to call
FLAC__seekable_stream_encoder_set_streamable_subset()

http://flac.sourceforge.net/api/group__flac__seekable__stream__encoder.html#a9

you can get error messages in string form with
FLAC__seekable_stream_encoder_get_resolved_state_string()

http://flac.sourceforge.net/api/group__flac__seekable__stream__encoder.html#a33

this will drill down into the underlying layers if necessary.

Josh



		
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