Write an audio data stream to file with GStreamer

[Markus Luttenberger]

Hey,


I read through the GStreamer manual and searched in the internet but I
don't really find a way to write an audio stream (bytes of audio data)
to a file, preferably a wav file.

I found a plugin called 'afsink' which seems to be able to write a wav
file. But I don't know what my data source shall be. Is there a sort of
buffer which I can hand over my data stream? Or can I directly feed the
sink? I only found examples which read audio data from a file!

Currently I'm using GStreamer 0.8.7 due restrictions. Please tell me if
this version is too old for this kind of job.


greetings..
..Markus

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[Markus Luttenberger]

Markus Luttenberger schrieb:
> I read through the GStreamer manual and searched in the internet but I
> don't really find a way to write an audio stream (bytes of audio data)
                                       ^^^^^^^^^^^^
> to a file, preferably a wav file.

Data from memory, to be more specific...



greetings..
..Markus

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[wl2776]

Markus Luttenberger wrote

Markus Luttenberger schrieb:
> I read through the GStreamer manual and searched in the internet but I
> don't really find a way to write an audio stream (bytes of audio data)
                                       ^^^^^^^^^^^^
> to a file, preferably a wav file.

Data from memory, to be more specific...

If your task as simple as just to encode audio samples from memory and write them to a file in any suitable format (WAV, ASF, MP3, something else), I'd recommend using FFmpeg and its API (libavformat, libavcodec, etc).

You just do the following:

//init.
av_register_all();
AVCodecContext *codec_ctx = avcodec_alloc_context();
AVCodec  *m_codec = avcodec_find_decoder(CODEC_ID_MJPEG);
avcodec_open(codec_ctx, codec);
uint8_t *buf;
short *samples;
int buf_size;
int bytes_used;

// allocate buf
// assign samples to point to your data

//encode
avcodec_encode_audio(codec_cts,buf,buf_size,samples);

//write buf to a disk


//cleanup
avcodec_close(codec_ctx);
av_free(codec_ctx);

Details are here:
http://cekirdek.pardus.org.tr/~ismail/ffmpeg-docs/avcodec_8h.html#c41ab8ea9bc0fd3bcf8dc9d3b446f5d3

Even simpler, you can exec ffmpeg and feed it with data via a pipe.

[Markus Luttenberger]

Vladimir Eremeev schrieb:

> Markus Luttenberger wrote:
>>> I read through the GStreamer manual and searched in the internet but I
>>> don't really find a way to write an audio stream (bytes of audio data)
>>                                        ^^^^^^^^^^^^
>>> to a file, preferably a wav file.
>> Data from memory, to be more specific...
>>
>
> If your task as simple as just to encode audio samples from memory and write
> them to a file in any suitable format (WAV, ASF, MP3, something else), I'd
> recommend using FFmpeg and its API (libavformat, libavcodec, etc).

Yes, I know it's quite simple. Actually, I've already done it using the
C library SNDFILE. But I need GStreamer as a cross-platform audio
library to play sound (also from memory!) and first I wanted to re-write
my WAVE file writer in order to get into GStreamer.

I cannot use FFmpeg because it's not installed. I am only allowed to
work with installed libraries that's why my GStreamer library is a
little bit old.

So, any specific tips for GStreamer?




greetings..
..Markus


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[Tim-Philipp Müller-2]

On Thu, 2009-12-17 at 15:03 +0100, Markus Luttenberger wrote:

Hi,

> I read through the GStreamer manual and searched in the internet but I
> don't really find a way to write an audio stream (bytes of audio data)
> to a file, preferably a wav file.
>
> I found a plugin called 'afsink' which seems to be able to write a wav
> file. But I don't know what my data source shall be. Is there a sort of
> buffer which I can hand over my data stream? Or can I directly feed the
> sink? I only found examples which read audio data from a file!
>
> Currently I'm using GStreamer 0.8.7 due restrictions. Please tell me if
> this version is too old for this kind of job.

GStreamer 0.8.7? From October 2004? Are you serious?

I'm fairly sure what you want to do is doable even with such an old
version. However, not only is that version more than five years old, but
we've also had a major API/ABI change since then, so don't be surprised
if no one remembers anything at all about 0.8.x.

If all you want to do is write raw audio PCM data to disk as a .wav
file, something like libsndfile might be a better fit. I wouldn't
recommend using an ancient and unsupported GStreamer version.

Cheers
 -Tim



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[wl2776]

Markus Luttenberger wrote

Vladimir Eremeev schrieb:
So, any specific tips for GStreamer?

Not so many. I'm not familiar with it.
You have to have a source, which would read your data from memory. Probably, you will have to write it yourself. And then, you'll need a sink, probably, autoaudiosink will do the job.
Then, you have to create a pipe, put everything in it, connect and run a pipe.

[Markus Luttenberger]

Tim-Philipp Müller schrieb:
> I'm fairly sure what you want to do is doable even with such an old
> version. However, not only is that version more than five years old, but
> we've also had a major API/ABI change since then, so don't be surprised
> if no one remembers anything at all about 0.8.x.

Yes, you're probably right. I will talk about an upgrade. If this is not
possible I'll have to stick to ALSA / DirectSound. And guess what, the
ALSA version is already five years old... :/



greetings..
..Markus


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