Recherche avancée

Sur d’autres sites (6591)

• avcodec/movtextdec : Fix immediately adjacent styles

  17 octobre 2020, par Andreas Rheinhardt

  avcodec/movtextdec : Fix immediately adjacent styles
  The checks for whether a style should be opened/closed at the current
  
  character position are as follows : A variable entry contained the index
  
  of the currently active or potentially next active style. If the current
  
  character position coincided with the start of style[entry], the style
  
  was activated ; this was followed by a check whether the current
  
  character position coincided with the end of style[entry] ; if so, the
  
  style was deactivated and entry incremented. Afterwards the char was
  
  processed.
  The order of the checks leads to problems in case the endChar of style A
  
  coincides with the startChar of the next style (say B) : Style B was never
  
  opened. When we are at said common position, the currently active style
  
  is A and so the start pos check does not succeed ; but the end pos check
  
  does and it closes the currently active style A and increments entry.
  
  At the next iteration of the loop, the current character position is
  
  bigger than the start position of style B (which is style[entry]) and
  
  therefore the style is not activated.
  The solution is of course to first check for whether a style needs to be
  
  closed (and increment entry if it does) before checking whether the next
  
  style needs to be opened.
  Reviewed-by : Philip Langdale <philipl@overt.org>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavcodec/movtextdec.c

• tools/target_dec_fuzzer : Adjust VQA threshold

  18 juillet 2020, par Michael Niedermayer

  tools/target_dec_fuzzer : Adjust VQA threshold
  Fixes : Timeout (169sec -> 9sec)
  
  Fixes : 23745/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_VQA_fuzzer-5638172179693568
  Found-by : continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] tools/target_dec_fuzzer.c

• FFMPEG :Adjusting PTS and DTS of encoded packets with real timestamps information

  19 août 2020, par jackey balwani

  I am trying to record a video of activities in desktop using muxing in FFMPEG Library.
I referred following link for my implementation.
https://ffmpeg.org/doxygen/trunk/muxing_8c_source.html

  


  I observe that the encoded video plays too fast. Below is the code of encoding the frame and then writing it to output file.

  


  static int write_frame(AVFormatContext *fmt_ctx, AVCodecContext *c,
                        AVStream *st, AVFrame *frame)
{
    int ret;
 
    // send the frame to the encoder
    ret = avcodec_send_frame(c, frame);
    if (ret < 0) {
    fprintf(stderr, "Error sending a frame to the encoder: %s\n",av_err2str(ret));
    exit(1);
    }
    while (ret >= 0) {
        AVPacket pkt = { 0 };

        ret = avcodec_receive_packet(c, &pkt);
        if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
           break;
        else if (ret < 0) {
           fprintf(stderr, "Error encoding a frame: %s\n", av_err2str(ret));
           exit(1);
        }

        /* rescale output packet timestamp values from codec to stream timebase(from 25 to 90000 this case) */
        av_packet_rescale_ts(&pkt, c->time_base, st->time_base);
        pkt.stream_index = st->index;

        /* Write the compressed frame to the media file. */
        log_packet(fmt_ctx, &pkt);
        ret = av_interleaved_write_frame(fmt_ctx, &pkt);
        av_packet_unref(&pkt);
        if (ret < 0) {
              fprintf(stderr, "Error while writing output packet: %s\n", av_err2str(ret));
              exit(1);
        }
    }
  
    return ret == AVERROR_EOF ? 1 : 0;
  }


  


  -> I am rescaling output packet timestamp values from codec to stream timebase (25 -> 90,000) before writing.
-> Since encoded video does plays very fast, so I have added temporary fix to multiply stream timebase by some factor just before av_packet_rescale_ts (in my case it is 5 -> 5*st->time_base.den which becomes 4,50,000) so that output video duration increases. This may not be the accurate solution as this would not give the real time shift between the frames.

  


  /**  rescale output packet timestamp values from codec to stream timebase  **/
st->time_base.den = 5*st->time_base.den;
av_packet_rescale_ts(pkt, *time_base, st->time_base);
pkt->stream_index = st->index;
/**  Write the compressed frame to the media file.  **/
return av_interleaved_write_frame(fmt_ctx, pkt);


  


  -> I want that output video duration should be similar to the input. I have heard of things like giving real timestamps to the PTS and DTS of frame and packets and encoding at variable or unknown frame rate.
Can we use these , If yes then How to implement ?
any suggestions or pseudo code of the approach would really help.

  


  Thanks