[LAD] Regarding amplifying a PCM frame

[Drip Stone]

and test .wav file is at
http://gamma.cs.unc.edu/SOUNDC/Assignments/clapping!_2.wav

On Mon, Oct 26, 2009 at 5:50 PM, Drip Stone
<dripstone.blendercn at gmail.com>wrote:

> Hello again,
>
> I obtain data for fbuffer in following way:
>     char *fbuffer = ( char * ) malloc ( 10240000 ); //10M bytes
>     long length = fread ( fbuffer, 1, 10240000, file );
>
> I also set alsa in float mode:
>     snd_pcm_hw_params_set_format ( handle, params,
>
>      SND_PCM_FORMAT_FLOAT_LE );
>
> I pasted all the code at http://pastebin.com/m7fdf0957.
>
>
> Thank you,
> Dripstone
>
>
>
> On Mon, Oct 26, 2009 at 3:59 PM, Jens M Andreasen <
> jens.andreasen at comhem.se> wrote:
>
>> Nothing in the posted code fragment suggests that neither in nor out is
>> remotely related to floats. Where do you get yor in-data from? Why is
>> fbuffer[] a bytearray (if that is what it is?) How was ALSA opened?
>>
>>
>> /j
>>
>> On Mon, 2009-10-26 at 15:05 -0700, Drip Stone wrote:
>>
>> >     while ( 1 )
>> >     {
>> >         for ( int i = 0; i < frames; i++ )
>> >         {
>> >             float t = 0;
>> >             if ( left )    //for left channel
>> >             {
>> >                 t = *((float*)&(fbuffer[pos+i*4]));    //4 bytes each
>> > frame
>> >                 t*=2;
>> >                 //printf("%f ",t);
>> >                 for ( int j = 0; j < 4; j++ )
>> >                     buffer[i*8+j] = ((char*)&t)[j];    //8 bytes for 2
>> > channels
>> >             }
>> >
>> >         rc = snd_pcm_writei ( handle, buffer, frames );
>> >         pos += frames * 4;
>> >     }
>> >
>> > I think the value is not out of [-1.0,1.0]. BTW, what does it mean
>> > when a value is negative?
>> >
>> >
>> > Best,
>> > Dripstone
>> >
>> > 2009/10/26 Jörn Nettingsmeier <nettings at folkwang-hochschule.de>
>> >         On 10/26/2009 11:38 AM, Victor Lazzarini wrote:
>> >         > Well if the audio was clipped, there would probably be some
>> >         audible
>> >         > distortion.
>> >         > Perhaps if a code fragment was posted we could give a more
>> >         informed
>> >         > opinion.
>> >
>> >
>> >         i was thinking of operating on files, where clamping can be
>> >         done with
>> >         perfect fidelity. but i may have misunderstood the OP.
>> >
>> >
>> >         _______________________________________________
>> >         Linux-audio-dev mailing list
>> >         Linux-audio-dev at lists.linuxaudio.org
>> >         http://lists.linuxaudio.org/mailman/listinfo/linux-audio-dev
>> >
>> >
>> > _______________________________________________
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>> > http://lists.linuxaudio.org/mailman/listinfo/linux-audio-dev
>>
>>
>
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