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• ffmpeg dash/hls wrong timestamp when using mp4, -ss, and -copyts

  6 décembre 2019, par user2114284

  I have noticed some inconsistencies with the output timestamp when using ffmpeg with the dash/hls muxers with mp4, -ss, and -coptyts and I am wondering if it is a bug or if I am just misunderstanding something about how ffmpeg is supposed to work.

  Here I seek 15 seconds in the input and use the copyts argument to copy the input timestamp :

  However, when checking the output with ffprobe, it shows the timestamps starting at 30 seconds, double what I would expect :

  ffmpeg -ss 15 -i big_buck_bunny_720p_10mb.mkv -to 30 -copyts -acodec aac -vcodec libx264 -f hls -hls_time 2 -hls_init_time 2 -hls_list_size 0 -hls_segment_type fmp4 out.m3u8
  
  
  
  cat init.mp4 out0.m4s | ffprobe -show_frames -pretty -
  
  
  
  [FRAME]
  
  media_type=video
  
  stream_index=0
  
  key_frame=1
  
  pkt_pts=384000
  
  pkt_pts_time=0:00:30.000000
  
  pkt_dts=384000
  
  pkt_dts_time=0:00:30.000000
  
  best_effort_timestamp=384000
  
  best_effort_timestamp_time=0:00:30.000000
  
  ...

  If I switch the hls_segment_type to mpegts, the timestamp shows around 15 seconds which I would expect :

  ffmpeg -ss 15 -i big_buck_bunny_720p_10mb.mkv -to 30 -copyts -acodec aac -vcodec libx264 -f hls -hls_time 2 -hls_init_time 2 -hls_list_size 0 -hls_segment_type mpegts out.m3u8
  
  
  
  ffprobe -i out0.ts -show_frames -pretty
  
  
  
  [FRAME]
  
  media_type=audio
  
  stream_index=1
  
  key_frame=1
  
  pkt_pts=1474080
  
  pkt_pts_time=0:00:16.378667
  
  pkt_dts=1474080
  
  pkt_dts_time=0:00:16.378667
  
  best_effort_timestamp=1474080
  
  best_effort_timestamp_time=0:00:16.378667
  
  ...

  I also see the timestamp being doubled when using -ss, -copyts, and mp4 with the dash muxer. Similarly, the dash muxer seems to output the correct timestamps when switched to webm.

  I have seen the same results with several different input files. Am I misunderstanding something about how ffmpeg works, or is this a bug somewhere in the mp4 segmenting ?

• MP4 to DASH using ffmpeg linux too slow

  16 mai 2022, par darox

  Currently, I'm working at a project that contains 2000 video mp4 files, and I need convert all of them in mpeg dash files.

  



  I have this script :

  



  MYDIR=$(dirname $(readlink -f ${BASH_SOURCE[0]}))
SAVEDIR=$(pwd)

# Check programs
if [ -z "$(which ffmpeg)" ]; then
    echo "Error: ffmpeg is not installed"
    exit 1
fi

if [ -z "$(which MP4Box)" ]; then
    echo "Error: MP4Box is not installed"
    exit 1
fi

cd "$MYDIR"

TARGET_FILES=$(find ./ -maxdepth 1 -type f \( -name "*.mov" -or -name "*.mp4" \))
for f in $TARGET_FILES
do
  fe=$(basename "$f") # fullname of the file
  f="${fe%.*}" # name without extension

  if [ ! -d "${f}" ]; then #if directory does not exist, convert
    echo "Converting \"$f\" to multi-bitrate video in MPEG-DASH"

    mkdir "${f}"

    ffmpeg -y -i "${fe}" -c:a aac -b:a 192k -vn "${f}_audio.m4a"


    ffmpeg -y -i "${fe}" -preset slow -tune film -vsync passthrough -write_tmcd 0 -an -c:v libx264 -x264opts 'keyint=25:min-keyint=25:no-scenecut' -crf 23 -maxrate 800k -bufsize 2000k -pix_fmt yuv420p -vf "scale=-2:720" -f mp4  "${f}_800.mp4"
    # static file for ios and old browsers and mobile safari
    ffmpeg -y -i "${fe}" -preset slow -tune film -movflags +faststart -vsync passthrough -write_tmcd 0 -c:a aac -b:a 160k -c:v libx264  -crf 23 -maxrate 1400 -bufsize 3000k -pix_fmt yuv420p -f mp4 "${f}/${f}.mp4"


    rm -f ffmpeg*log*
    # if audio stream does not exist, ignore it
    if [ -e "${f}_audio.m4a" ]; then
        MP4Box -dash-strict 2000 -rap -frag-rap  -bs-switching no -profile "dashavc264:live" "${f}_5000.mp4" "${f}_3000.mp4" "${f}_1500.mp4" "${f}_800.mp4" "${f}_400.mp4" "${f}_audio.m4a" -out "${f}/${f}.mpd"
        rm "${f}_5000.mp4" "${f}_3000.mp4" "${f}_1500.mp4" "${f}_800.mp4" "${f}_400.mp4" "${f}_audio.m4a"
    else
        MP4Box -dash-strict 2000 -rap -frag-rap  -bs-switching no -profile "dashavc264:live" "${f}_5000.mp4" "${f}_3000.mp4" "${f}_1500.mp4" "${f}_800.mp4" "${f}_400.mp4" -out "${f}/${f}.mpd"
        rm "${f}_5000.mp4" "${f}_3000.mp4" "${f}_1500.mp4" "${f}_800.mp4" "${f}_400.mp4" 
    fi
    # create a jpg for poster. Use imagemagick or just save the frame directly from ffmpeg is you don't have cjpeg installed.
    ffmpeg -i "${fe}" -ss 00:00:00 -vframes 1  -qscale:v 10 -n -f image2 - | cjpeg -progressive -quality 75 -outfile "${f}"/"${f}".jpg

    fi

done

cd "$SAVEDIR"


  



  This is working fine, but, taking a long time to convert only single file, I have intel 7 and a simple mp4 file take 30 min to be converted. How can I accelerate this process ? Must I change something in this script ?

  



  Thank you.

  


• avcodec/hevc_sei : replace en dash character with a hyphen

  6 décembre 2020, par James Almer

  avcodec/hevc_sei : replace en dash character with a hyphen
  Signed-off-by : James Almer <jamrial@gmail.com>
  

  • [DH] libavcodec/hevc_sei.c