Re: [FFmpeg-trac] #9210(undetermined:new): Concat images produces wrong timings when duration is in milliseconds

6 Dec 2021

      #9210: Concat images produces wrong timings when duration is in milliseconds
-------------------------------------+-------------------------------------
             Reporter:  demet64      |                    Owner:  (none)
                 Type:  defect       |                   Status:  new
             Priority:  normal       |                Component:
                                     |  undetermined
              Version:  unspecified  |               Resolution:
             Keywords:  concat       |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
Comment (by Andre LaBranche):

 The unwanted 25 fps does seem to be coming from `concat`. I tested that
 along with `image2` and found that `image2` honors the frame rate passed
 as a cli option.

 Here's a script that creates some sample images, does a concat run and an
 image2 run, and collects reports for each.

 {{{
 #!/bin/zsh

 OUT=$(mktemp -d)
 CATFILE=${OUT}/catfile.txt
 pushd ${OUT}
 echo "generating some sample images with Imagemagik's 'convert' tool"
 for i in {1..60}
 do
     IMG=image-$(printf "%03d" ${i}).jpg
     convert -size 600x300 -gravity center -background black \
         -fill purple label:${i} -units PixelsPerInch -density 254 ${IMG}
     echo "file '${IMG}'" >> ${CATFILE}
     echo "duration 0.016" >> ${CATFILE}
 done

 echo "Wrote sample ffmpeg concat input file: ${CATFILE}"

 CONCAT_CMD='ffmpeg -f concat -i ${CATFILE} -report concat.mkv 2>
 /dev/null'
 export FFREPORT=file=ffprobe-concat.log
 echo "Probing concat with:\n${CONCAT_CMD}"
 eval ${CONCAT_CMD}
 echo "Wrote video ${OUT}/concat.mkv"
 echo "Reading frame rate of concat.mkv..."
 ffprobe -v error -show_format -show_streams concat.mkv | grep 'frame_rate'

 IMAGE2_CMD="ffmpeg -f image2 -framerate 60 -i image-%03d.jpg image2.mkv 2>
 /dev/null"
 echo "\nProbing image2 with:\n${IMAGE2_CMD}"
 export FFREPORT=file=ffprobe-image2.log
 eval ${IMAGE2_CMD}
 echo "Wrote video ${OUT}/image2.mkv"
 echo "Reading frame rate of concat.mkv..."
 ffprobe -v error -show_format -show_streams image2.mkv | grep 'frame_rate'
 echo "\nFull reports for each run: "
 ls -1 ${OUT}/ffprobe*.log
 open ${OUT}
 popd
 }}}

 When run on my machine, it looks like this:

 {{{
 andre@boom  % ./duration_snooping.sh
 generating some sample images with Imagemagik's 'convert' tool
 Wrote sample ffmpeg concat input file:
 /var/folders/sc/q27bbsbn105gr0d08r3nd2jr0000gn/T/tmp.jAH5RBjv/catfile.txt
 Probing concat with:
 ffmpeg -f concat -i ${CATFILE} -report concat.mkv 2> /dev/null
 Wrote video
 /var/folders/sc/q27bbsbn105gr0d08r3nd2jr0000gn/T/tmp.jAH5RBjv/concat.mkv
 Reading frame rate of concat.mkv...
 r_frame_rate=25/1
 avg_frame_rate=25/1

 Probing image2 with:
 ffmpeg -f image2 -framerate 60 -i image-%03d.jpg image2.mkv 2> /dev/null
 Wrote video
 /var/folders/sc/q27bbsbn105gr0d08r3nd2jr0000gn/T/tmp.jAH5RBjv/image2.mkv
 Reading frame rate of concat.mkv...
 r_frame_rate=60/1
 avg_frame_rate=60/1

 Full reports for each run:
 /var/folders/sc/q27bbsbn105gr0d08r3nd2jr0000gn/T/tmp.jAH5RBjv/ffprobe-
 concat.log
 /var/folders/sc/q27bbsbn105gr0d08r3nd2jr0000gn/T/tmp.jAH5RBjv/ffprobe-
 image2.log
 }}}

 Here are the two reports from the above run:

 * https://youbeill.in/scrap/ffprobe-image2.log
 * https://youbeill.in/scrap/ffprobe-concat.log
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/9210#comment:7>
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