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• avcodec/asvenc : Don't waste bits encoding non-visible part

  22 mai, par Andreas Rheinhardt

  avcodec/asvenc : Don't waste bits encoding non-visible part
  Up until now, the encoder replicated all the border pixels
  
  for incomplete 16x16 macroblocks. In case the available width
  
  or height is <= 8, some of the luma blocks of the MB
  
  do not correspond to actual input, so that we should encode
  
  them using the least amount of bits. Zeroing the block coefficients
  
  (as this commit does) achieves this, replicating the pixels
  
  and performing an FDCT does not.
  This commit also removes the frame copying code for insufficiently
  
  aligned dimensions.
  The vsynth3-asv[12] FATE tests use a 34x34 input file and are
  
  therefore affected by this. As the ref updates show, the size
  
  and checksum of the encoded changes, yet the decoded output
  
  stays the same.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavcodec/asvenc.c
  • [DH] tests/ref/vsynth/vsynth3-asv1
  • [DH] tests/ref/vsynth/vsynth3-asv2

• Hit noise when playing part of wave file with ALSA PCM interface

  11 décembre 2024, par wangt13

  I am working a WAVE file playing with ALSA PCM interface in Linux, and I heard noise when I played the file quickly and partially.

  


  Here is my playing function.

  


  static int playback_function(uint8_t *pcm_buf, int pcm_frames)
{
    int  rc;
    uint8_t *buf;
    int frame_size, sent;
    int periodsize;
    int left;

    frame_size = chan * av_get_bytes_per_sample(AV_SAMPLE_FMT_S16);
    periodsize = sys_periodsize; // 320 in my system
    buf = pcm_buf;
    left = pcm_frames;
    sent = 0;

    while (left > 0) {
        sent = (left > periodsize) ? periodsize : left;
        rc = snd_pcm_writei(pcm_handle, buf, sent);
        printf("rc: %d, sent: %d\n", rc, sent);
        if (rc == -EAGAIN || (rc >= 0 && (size_t)rc < sent)) {
            snd_pcm_wait(pcm_handle, 10);
        } else if (rc == -EPIPE) {
            snd_pcm_recover(pcm_handle, rc, 0);
        } else if (rc < 0) {
            break;
        }
        if (rc > 0) {
            left -= rc;
            buf += rc * frame_size;
        }
    }
    return rc;
}


  


  The pcm_buf and pcm_frames are got from swr_convert() in libswresample, in my case, the pcm_frames is 1187.

  


  By adding printf("rc: %d, sent: %d\n", rc, sent);, I got following logs.

  


  rc: 320, sent: 320
rc: 87, sent: 87
rc: 320, sent: 320
rc: 320, sent: 320
rc: 103, sent: 103
rc: 320, sent: 320
rc: 320, sent: 320
rc: 103, sent: 103
rc: 320, sent: 320
rc: 320, sent: 320
rc: 103, sent: 103
rc: 320, sent: 320
rc: 320, sent: 320
rc: 103, sent: 103
rc: 320, sent: 320
rc: 320, sent: 320
rc: 103, sent: 103
rc: 320, sent: 320
rc: 320, sent: 320
rc: 103, sent: 103
rc: 320, sent: 320
rc: 320, sent: 320
rc: 103, sent: 103
rc: 320, sent: 320
rc: 320, sent: 320
rc: 103, sent: 103
rc: 320, sent: 320
rc: 320, sent: 320
rc: 87, sent: 87
rc: 320, sent: 320
rc: 320, sent: 320
rc: 103, sent: 103


  


  With above function, sometimes I can hear noise when playing the WAVE file quickly and repeatly.
  
So, how can I improve the WAVE playing without the noise ??

  


  I changed the above function by using filling 0 to the end of data buffer (to enforce silence).

  


  static int playback_test(uint8_t *pcm_buf, int pcm_frames)
{
    uint8_t *buf;
    int trd;
    int rc;
    int left;
    int frame_size, sent;
    int periodsize;
    int aligned = 0;

    frame_size = chan * av_get_bytes_per_sample(AV_SAMPLE_FMT_S16);
    periodsize = sys_periodsize; // 320 in my system

    buf = pcm_buf;
    left = pcm_frames;
    aligned = (left/periodsize + 1) * periodsize;
    memset(buf + left * frame_size, 0, (aligned - left) * frame_size);
    sent = 0;
///left = periodsize; // <== This causes more noise!!

    while (left > 0) {
        sent = (left > periodsize) ? periodsize : left;
        rc = snd_pcm_writei(pcm_handle, buf, sent);
        printf("rc: %d, sent: %d\n", rc, sent);
        if (rc == -EAGAIN || (rc >= 0 && (size_t)rc < sent)) {
            snd_pcm_wait(pcm_handle, 10);
        } else if (rc == -EPIPE) {
            snd_pcm_recover(pcm_handle, rc, 0);
        } else if (rc < 0) {
            break;
        }
        if (rc > 0) {
            left -= rc;
            buf += rc * frame_size;
        }
    }
    return rc;
}


  


  There is NO improvement as of the noise.

  


• jpeg2000dec : fix tile-part header state reset

  24 octobre 2024, par Pierre-Anthony Lemieux

  jpeg2000dec : fix tile-part header state reset
  Fixes https://trac.ffmpeg.org/ticket/11266
  

  • [DH] libavcodec/jpeg2000dec.c
  • [DH] libavcodec/jpeg2000dec.h