[alsa-devel] snd_pcm_mmap_commit

[Irfan Shaikh]

/*************************************************************/
Code below O/p results runs in a while loop till end of PCM data.
1) First time O/p is
          Farames available : 1024                                                /*Return VALUE of snd_pcm_avail_update*/
          >>>>>>>>>>>>>>>>>>>>>>>>>Begin result : 0      /*Return VALUE of snd_pcm_mmap_begin*/
          Address outbuffer : 0xcff88
          >>>>>>>>>>>>>>>>>>>>>>Comit result : 1024       /*SUCESSFUL - Return VALUE of  snd_pcm_mmap_commi*/

2) Second time onwards ALWAYS O/p is
          Farames available : 0                                                      /*Return VALUE of snd_pcm_avail_update*/
          >>>>>>>>>>>>>>>>>>>>>>>>>Begin result : 0      /*Return VALUE of snd_pcm_mmap_begin*/
          Address outbuffer : 0xcff88
          >>>>>>>>>>>>>>>>>>>>>>Comit result : 0             /*FAILURE - Return VALUE of  snd_pcm_mmap_commit*/
.
.
.
.
.
.
N) Nth time
          Farames available : 0                                                      /*Return VALUE of snd_pcm_avail_update*/
           >>>>>>>>>>>>>>>>>>>>>>>>>Begin result : 0      /*Return VALUE of snd_pcm_mmap_begin*/
          Address outbuffer : 0xcff88
          >>>>>>>>>>>>>>>>>>>>>>Comit result : 0              /*FAILURE - Return VALUE of  snd_pcm_mmap_commit*/
.
/*************************************************************/
+++++++++++++++
 Why  second time onwards I get the above behavious what am i missing ? Please HELP  !
+++++++++++++++

############ MY CODE #############

#ifdef DIRECT
        snd_pcm_sframes_t frames_available, frames_transmit;
        const snd_pcm_channel_area_t *area;
        snd_pcm_uframes_t offset;
        unsigned char *outbuffer;
        int result,i;

        /*available space in audio-buffer to write to*/
        frames_available = snd_pcm_avail_update(alsaParams->pcm_handle);
        printf("Farames available : %d\n", frames_available);

        /*
         * prepare the areas
         * and get back area, offset and frames_transmit
         * frames_transmit gives back the REAL value of available frames which could be written to in the mmaped-area
         * frames_transmit are less than frames_available
         */
        frames_transmit = frames_available;

        if( 0 > ( result = snd_pcm_mmap_begin(alsaParams->pcm_handle, &area, &offset, &frames_transmit)))
        {
            printf("===========================>>>>>>>>>>>>>>>>>>>>>snd_pcm_mmap_begin_error\n");
            xrun_recovery(alsaParams->pcm_handle, pcmreturn);
            return;
            //return xrun_recovery();
        }

        printf(">>>>>>>>>>>>>>>>>>>>>>>>>Begin result : %d\n", result);
        utbuffer = ((char *) area->addr + (area->first + area->step * offset)/ 8);
        printf("Address outbuffer : %p\n", outbuffer);

        memcpy(outbuffer, data, count);  //data is actual data

        /*gives back the virtually written (writable) frames which should be always == frames_transmit*/
        if( 0 > ( result = snd_pcm_mmap_commit(alsaParams->pcm_handle, offset, frames_transmit)))
        {
            printf("==============================>>>>>>>>>>>>>>>>>>>>>>>>snd_pcm_mmap_commit error\n");
            xrun_recovery(alsaParams->pcm_handle, pcmreturn);
            return;
            //return xrun_recovery();
        }
        printf(">>>>>>>>>>>>>>>>>>>>>>Comit result : %d\n", result);
#endif

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