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• How do I make a bash script continue part of a loop only if there is no error in the first step of the loop ?

  30 mars 2012, par Eli Greenberg

  I currently have a .command file for Mac that contains the following :

  for f in ~/Desktop/Uploads/*.flv
  
  do
  
       /usr/local/bin/ffmpeg -i "$f" -vcodec copy -acodec libfaac -ab 128k -ar 48000 -async 1 "${f%.*}".mp4
  
       rmtrash "$f"
  
  done

  How can I tell bash to only execute rmtrash if ffmpeg doesn't produce an error ?

• 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.

  


• How do I add a text for the 1st 30 seconds inside a filter_complex expression for each video part ?

  30 décembre 2022, par PirateApp

  I am generating a video grid using the following filter_complex command

  


  ffmpeg
     -i v_nimble_guardian.mkv -i macko_nimble_guardian.mkv -i ghost_nimble_guardian_1.mp4 -i nano_nimble_guardian.mkv
     -filter_complex "
         nullsrc=size=3840x2160 [base];
         [0:v] trim=start=39.117000,setpts=PTS-STARTPTS, scale=1920x1080 [upperleft];
         [1:v] trim=start=40.483000,setpts=PTS-STARTPTS, scale=1920x1080 [upperright];
         [2:v] trim=start=32.416471,setpts=PTS-STARTPTS, scale=1920x1080 [lowerleft];
         [3:v] trim=start=28.100000,setpts=PTS-STARTPTS, scale=1920x1080 [lowerright];
         [3:a] atrim=start=28.100000,asetpts=PTS-STARTPTS[outa];
         [base][upperleft] overlay=shortest=1 [tmp1];
         [tmp1][upperright] overlay=shortest=1:x=1920 [tmp2];
         [tmp2][lowerleft] overlay=shortest=1:y=1080 [tmp3];
         [tmp3][lowerright] overlay=shortest=1:x=1920:y=1080[v]
     "
     -map "[v]" -map "[outa]" -c:v libx264 -crf 17 -shortest -t 880 output4k.mkv


  


  How do I text to this video grid that will appear with a fade in at 10 seconds, stay for 30 seconds and then fade out ?

  


  

  


  What I tried ?

  


  ffmpeg
     -i v.mkv -i macko_nimble_guardian.mkv -i ghost_nimble_guardian_subtle_arrow_1.mp4 -i nano_nimble_guardian.mkv
     -filter_complex "
         nullsrc=size=1920x1080 [base];
         drawtext=text='Summer Video':enable='between(t,10,30)'[fg];
         [0:v] trim=start=39.117000,setpts=PTS-STARTPTS, scale=960x540 [upperleft];
         [1:v] trim=start=40.483000,setpts=PTS-STARTPTS, scale=960x540 [upperright];
         [2:v] trim=start=32.416471,setpts=PTS-STARTPTS, scale=960x540 [lowerleft];
         [3:v] trim=start=28.100000,setpts=PTS-STARTPTS, scale=960x540 [lowerright];
         [3:a] atrim=start=28.100000,asetpts=PTS-STARTPTS[outa];
         [base][upperleft] overlay=shortest=1 [tmp1];
         [tmp1][upperright] overlay=shortest=1:x=960 [tmp2];
         [tmp2][lowerleft] overlay=shortest=1:y=540 [tmp3];
         [tmp3][lowerright] overlay=shortest=1:x=960:y=540[v]
     "
     -map "[v]" -map "[outa]" -c:v libx264 -shortest -t '30' output2.mkv


  


  It gives me an error

  


  [Parsed_drawtext_1 @ 0x600002bdc420] Using "/System/Library/Fonts/Supplemental/Verdana.ttf"
Filter drawtext:default has an unconnected output