unable to write FLAC files with SoundFile

[raecke]

The script

import soundfile as sf
sf.write('test.flac', [0.1, 0.2, 0.3, 0.4], 48000)

crashes with the current master branch of SoundFile, and python 2.7.6 (32-bit) under Windows 7 64bit.

Also affected is tag 1.0.27. Tag 1.0.25 works.

[mgeier]

It would be interesting to know if it works with the DLLs from the original installer: http://www.mega-nerd.com/libsndfile/#Download

[raecke]

It also fails.

It is quite weird, that it works if I type the commands in the python command interpreter, but it fails when I execute it in a script.

[mgeier]

That's indeed weird. Did you make sure that you are using the same Python version in both cases?

There might be a problem when closing the interpreter, you could try to add time.sleep(3) at the end of your script or something like input(). You could also try to start it with python3 -i myscript.py.

How does the crash look like? Is there an error message?
Is the output sound file written correctly or not?

[raecke]

There might be a problem when closing the interpreter, you could try to add time.sleep(3) at the end of your script or something like input(). You could also try to start it with python3 -i myscript.py.

This did not help. If I change the script into:

import soundfile as sf
sf.write('test.flac', [x/10.0 for x in range(4097)], 48000)

it also fails when I type the commands in the python interpreter (It does not fail if the length is 4096 samples).

I get no error message from python. The Windows operating system says that python.exe does not work anymore. The output file is only an empty FLAC file.

[mgeier]

OK, can you please summarize in which exact combinations it works and in which it doesn't?
Can you please also try the update-to-1.0.26 branch?
Can you try on a 64-bit Python?

I think in the end we should try to reproduce the problem with a little example program written in C and then report it to the libsndfile issue tracker (if it still occurs).
Do you have the possibility to compile a C program and link it to a given libsndfile DLL?

[raecke]

OK, can you please summarize in which exact combinations it works and in which it doesn't?

The 32-bit version fails, if the buffer is big enough. The exact buffer size needed for failure is unclear.

I made a simple test program in C, and compiled it using Visual Studio 2013.

32-bit: fails with libsndfile DLL > 1.0.25. The debugger says: Unhandled exception at 0x56B71112 (libsndfile-1.dll) in testlibsndfile.exe: 0xC0000005: Access violation reading location 0x00000000.
64-bit: works

If I change the output format to: sfinfo.format = SF_FORMAT_OGG | SF_FORMAT_VORBIS;, then it fails
with 32-bit and 64-bit (every DLL version 1.0.25--1.0.28). The debugger says: Unhandled exception at 0x000000006480E9D6 (libsndfile-1.dll) in testlibsndfile.exe: 0xC00000FD: Stack overflow (parameters: 0x0000000000000001, 0x0000000000223980).

#include <string.h>
#include <stdlib.h>
#include "sndfile.h"

#define NUMBER_OF_SAMPLES 480000
double buffer[NUMBER_OF_SAMPLES];
const char* outfilename = "test";

int main(int argc, char* argv[])
{
	SNDFILE		*outfile;
	SF_INFO		sfinfo;
	unsigned int i;

	memset(&sfinfo, 0, sizeof(sfinfo));
	sfinfo.format = SF_FORMAT_FLAC | SF_FORMAT_PCM_16;
	sfinfo.channels = 1;
	sfinfo.samplerate = 48000;
	if (!sf_format_check(&sfinfo)) {
		printf("Invalid encoding\n");
		return 2;
	}

	if (!(outfile = sf_open(outfilename, SFM_WRITE, &sfinfo))) {
		printf("Error : could not open file : %s\n", outfilename);
		puts(sf_strerror(NULL));
		return 1;
	}

	for (i = 0; i < NUMBER_OF_SAMPLES; ++i)
		buffer[i] = i *1.0 / NUMBER_OF_SAMPLES;
	sf_write_double(outfile, buffer, NUMBER_OF_SAMPLES);

	sf_close(outfile);
	printf("ok\n");
	return 0;
}

#pragma comment(lib, "libsndfile-1.lib")

[mgeier]

@raecke So this error also happens with the library files from the original libsndfile installer, right?

I think you should raise an issue at libsndfile project: https://github.com/erikd/libsndfile/issues

[mgeier]

See also:

• Converting Wav to Flac introduces strange artifacts. python-soundfile#265
• -1. sometimes flips to 1. when reading FLAC format python-soundfile#274
• Unable to complete round trip tests for a FLAC File using libsnd library libsndfile/libsndfile#504