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• FFMPEG add black bars to a image if the video input is not 16:9

  31 décembre 2020, par iTeY

  So I'm playing with ffmpeg and I have the command currently :

  


  "ffmpeg_path -ss seek_time -i input_video_path -vframes 1 -f mjpeg output_image_path 2<&1"


  


  The issue that I'm facing is that for example I have a vertical video from a mobile phone the output image will be streched to 16:9, what I would like to do is to add black bars to the side of the image if the input is not in a 16:9 format.

  


  Any suggestions or ideas on how I could do that ?

  


  Thank you !

  


• How to trim a video file at a precise position without re-encoding using FFMPEG [closed]

  2 août 2024, par Wassim Erriha

  I am having trouble trimming video files without causing the Video/Audio to go out of sync.
From what I understand, using the seek argument -ss before or after the input file results in two different behaviors. 
For Example :

  



  ffmpeg  -ss 00:00:00.600 -i in.mp4 -c copy out.mp4 


  



  This produces a trim with accurate A/V sync but a rough audio trim (trim happens at a video key frame and not the precise seek value)

  



  ffmpeg  -i in.mp4 -ss 00:00:00.600 -c copy out.mp4


  



  This produces a more accurate audio trim but causes A/V to go out of sync. Frames after the trim position are dependent on frames before the trim position.These frames are assigned negative timestamps and copied to output file, which results in video being out of sync with audio during playback.

  



  On the other hand,

  



  ffmpeg  -i "in.mp4" -ss 00:00:00.600 -strict -2 out.mp4


  



  This produces a more precise trimming and A/V sync.
The trim task takes a long time to run and results in quality loss.

  



  My Question is :
Is there a way to get an accurate trim without re-encoding the video ?
maybe by discarding the extra frames at the beginning that cause the A/V to get out of sync.
In my case, I can live with a few black frames in the beginning, as long as the audio is trimmed at the precise position and A/V sync is preserved.
Is it possible to accomplish this using FFMPEG ?
if not, can MediaCodec on Android handle such precision when trimming ?

  



  Thanks for your time.

  


• 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.