[flac-dev] Crash when writing 32bit flac files, am I doing something wrong ?

[lvqcl]

On Thu, Mar 22, 2018 at 3:41 AM, Stéphane Damo <stephane.damo at gmail.com> wrote:
> Hello,
>
> I manage to successfully write 8, 16 and 24 bit, all stereo, FLAC files. But
> when I try to write 32 bit FLACs my program crashes.
>
> FLAC__stream_encoder_set_bits_per_sample is called to match the desired bit
> depth (8, 16, 24, 32)
>
> It's the same code for all bit depths, i provide a fixed-size signed int
> buffer to the lib (size=16384), with values with appropriate ranges for each
> bit depth (-128...+127 for 8 bit, etc.).
>
> The crash happens in stream_encoder.c line 2263 :
>
> encoder->private_->integer_signal[channel][i] = buffer[k++];
>
> It happens when I call FLAC__stream_encoder_process_interleaved(encoder,
> out, 16384/2) in my code. Its working perfectly for all bit depth except 32
> bit.
>
>
> Output message: Unhandled exception at 0x00F98441 in fmcomposer.exe:
> 0xC0000005: Access violation writing location 0x00000000.
>
>
> I'm using the latest code from the github repository. Reading the docs
> didn't noticed any thing special to do for writing 32 bit FLACs, it seems it
> should be supported. Maybe I am missing something ?

AFAIK: while FLAC format itself supports 32-bit PCM, the official
encoder doesn't support it.

from include/FLAC/format.h:


/** The maximum sample resolution permitted by the format. */
#define FLAC__MAX_BITS_PER_SAMPLE (32u)

/** The maximum sample resolution permitted by libFLAC.
 *
 * \warning
 * FLAC__MAX_BITS_PER_SAMPLE is the limit of the FLAC format.  However,
 * the reference encoder/decoder is currently limited to 24 bits because
 * of prevalent 32-bit math, so make sure and use this value when
 * appropriate.
 */
#define FLAC__REFERENCE_CODEC_MAX_BITS_PER_SAMPLE (24u)

also, init_stream_internal_() function already checks bit depth:

    if(encoder->protected_->bits_per_sample <
FLAC__MIN_BITS_PER_SAMPLE || encoder->protected_->bits_per_sample >
FLAC__REFERENCE_CODEC_MAX_BITS_PER_SAMPLE)
        return FLAC__STREAM_ENCODER_INIT_STATUS_INVALID_BITS_PER_SAMPLE;


so, maybe you forgot to check return value for errors?