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• FFmpeg HLS streaming - Why the program date time of older segment changing when re-streaming after discontinuity

  9 novembre 2020, par Suriya Krish

  Following is the ffmpeg command to stream the data.

  


  ffmpeg -re -f avfoundation 
-framerate 30 -i 0 
-codec:v h264_videotoolbox -x264-params keyint=120:scenecut=0 
-codec:a copy -f hls 
-hls_list_size 60 
-hls_time 10 
-hls_flags delete_segments 
-hls_flags +append_list 
-hls_flags +discont_start 
-hls_flags +program_date_time 
-strftime 1 
-strftime_mkdir 1 
-hls_segment_filename 
'%Y%m%dT%H%M%S%z.ts' playlist.m3u8


  


  Following is the playlist.m3u8 content which generated for few seconds.

  


  #EXTM3U
#EXT-X-VERSION:3
#EXT-X-TARGETDURATION:10
#EXT-X-MEDIA-SEQUENCE:0
#EXT-X-DISCONTINUITY
#EXT-X-DISCONTINUITY
#EXTINF:10.000000,
#EXT-X-PROGRAM-DATE-TIME:2020-11-09T22:07:53.000+0530
20201109T220753+0530.ts
#EXTINF:10.000000,
#EXT-X-PROGRAM-DATE-TIME:2020-11-09T22:08:03.000+0530
20201109T220803+0530.ts
#EXT-X-ENDLIST


  


  When the re-stream happens(in case of restarting the streaming service), the program date time of older segments(before #EXT-X-DISCONTINUITY) also get changed like below, which is unexpected.

  


  #EXTM3U
#EXT-X-VERSION:3
#EXT-X-TARGETDURATION:10
#EXT-X-MEDIA-SEQUENCE:0
#EXT-X-DISCONTINUITY
#EXT-X-DISCONTINUITY
#EXTINF:10.000000,
#EXT-X-PROGRAM-DATE-TIME:2020-11-09T22:12:50.633+0530
20201109T220753+0530.ts
#EXTINF:10.000000,
#EXT-X-PROGRAM-DATE-TIME:2020-11-09T22:13:00.633+0530
20201109T220803+0530.ts
#EXT-X-DISCONTINUITY
#EXTINF:10.000000,
#EXT-X-PROGRAM-DATE-TIME:2020-11-09T22:13:12.000+0530
20201109T221312+0530.ts
#EXTINF:5.400000,
#EXT-X-PROGRAM-DATE-TIME:2020-11-09T22:13:22.000+0530
20201109T221322+0530.ts
#EXT-X-ENDLIST


  


  Why the program date time of older segment should change ? Should we add any arguments in ffmpeg command to handle this ?

  


• Converting bat to bash script [on hold]

  15 juillet 2019, par dezxela

  Please help me with coversion this script from here to bash :
  https://stackoverflow.com/a/38291960/11786146

  This part of the code seems to be reconciled in me, but I’m not sure that it’s correct :

  #  path to ffmpeg
  
  export  ffmpeg='/home/user/bin'
  
  #  source movies from
  
  export  movieSource='/mnt/dev1/radio/Masha'
  
  #  tmp dir
  
  export  tmpDir='/mnt/dev1/radio/Masha'
  
  
  
  
  
  #  setup positon, color, background, font for the text overlays
  
  #  filterComplex, quotes have to be escaped! -> \"
  
  #  BITC - Burned In Time Code
  
  export  filterComplexTimecode='drawtext=fontfile='/usr/share/fonts/truetype/freefont/FreeSerif.ttf': timecode='10\:00\:00\:00': timecode_rate=24: x=(w-tw)/2: y=h-(1*lh)-3: fontsize=20: fontcolor=white@0.4: box=1: boxcolor=0x00000000@0.4: boxborderw=4'
  
  #  Date
  
  export  filterComplexDate='drawtext=fontfile='/usr/share/fonts/truetype/freefont/FreeSerif.ttf': text='%{localtime\:%X}': x=(w-tw-3): y=h-(1*lh)-3: fontsize=20: fontcolor=white@0.4: box=1: boxcolor=0x00000000@0.4: boxborderw=4'
  
  #  Shotname
  
  export  filterComplexShotname='drawtext=fontfile='/usr/share/fonts/truetype/freefont/FreeSerif.ttf': x=0: y=h-(1*lh)+1: fontsize=20: fontcolor=white@0.4: box=1: boxcolor=0x00000000@0.4: boxborderw=4:'
  
  
  
  #  create a list of all files
  
  find "$movieSource" -name "*.mp4" -type f | sort -R | while read j; do echo "file '$j'" >> $tmpDir/filelist.txt; done
  
  
  
  echo filename, durationInSeconds > $tmpDir/fileNameDuration.txt
  
  for file in $movieSource/*.mp4; do
  
    #  Reset current duration to 0 (zero) for each loop
  
    export  curDuration=0
  
    #  get the filename without file extenion
  
    export  fileName=${file##*/}
  
    #  get the duration of a single clip
  
    #  and write it to a tmp textfile
  
    $ffmpeg/ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 "$file" > $tmpDir/fileTempDuration.txt
  
    #  read the textfile again into a variable
  
   read -p  < $tmpDir/fileTempDuration.txt last curDuration
  
  
  
    #  write the filename and the duration to a new list of all files
  
  echo $fileName,$curDuration >> $tmpDir/fileNameDuration.txt ;done
  
  
  
  #  concate a filter complex string for ffmpeg with all clipnames as textlayer with a inpoint and outpoint
  
  export  filterComplexShotnameCombined=
  
  #  floating numbers are not supported by batch, so we need to work-around that
  
  source  :IntAsFP b=0.000000
  
  for i in $tmpDir/fileNameDuration.txt; do
  
    source  :IntAsFP a=$j
  
    source  :IntToFP inPoint=$b 6
  
    export  c=$(expr a + b)
  
    export   b=c
  
    source  :IntToFP outPoint=$c 6
  
    #  just to check whats going on...
  
    echo name: $i   duration: $j   inPoint: $inPoint   outPoint: $outPoint
  
    export  filterComplexShotnameCombined='$filterComplexShotnameCombined, $filterComplexShotname text=$i: enable=between(t\,$inPoint\,$outPoint^^^)';done

• when ffpmeg drops frames some things aren't played back in real time

  8 février 2024, par Alex028502

  I am trying to run a bunch of ffpmeg processes that act as simulators for cameras, and something funny is happening when I the processor can't keep up with the configured frame rate.

  


  I have replaced the rtsp stream with an output file, and managed to reproduce the issue, so will just show that to keep it simple.

  


  First here is a makefile that creates my source movie :

  


  clock.mp4: Makefile
    rm -f $@
    ffmpeg -f lavfi -i color=c=black:s=4096x2160:r=25 -vf \
"drawtext=fontfile=/usr/share/fonts/truetype/dejavu/DejaVuSans-Bold.ttf:fontsize=72:fontcolor=white:x=(w-text_w)/2:y=(h-text_h)/2: \
text='%{eif\:trunc(n/25)\:d}':start_number=0:rate=25" \
-t 60 -r 25 $@


  


  that gives me a one minute long movie that prints the second number to the screen. I have tested it out and the seconds are close enough. I put a lot of pixels to make it easier to jam up my CPU.

  


  Here is the script that creates a processes similar to the one I am trying to debug (called experiment.sh)

  


  I am actually using H.264, but H.265 is easier to overwhelm the processor with

  


  #! /usr/bin/env bash

set -e

echo starting > message$1.txt

rm -f superclock$1.mp4
ffmpeg -re -stream_loop -1 -i clock.mp4 \
       -an -vcodec libx265 -preset ultrafast -sc_threshold -1 -x265-params repeat-headers=1 \
       -vf "drawtext=fontfile=/usr/share/fonts/truetype/dejavu/DejaVuSans-Bold.ttf:fontsize=24:fontcolor=white:x=10:y=10:text='%{localtime\:%X}', \
            drawtext=fontfile=/usr/share/fonts/truetype/dejavu/DejaVuSans-Bold.ttf:fontsize=24:fontcolor=white:x=10:y=(h-text_h-10):textfile=message$1.txt:reload=1, \
            scale=1920x1080,fps=25" \
       -b:v 3M -minrate 3M -maxrate 3M \
       -bufsize 6M -g 25 superclock$1.mp4 &
pid=$!

for x in $(seq 0 10)
do
    echo $x > message$1.txt
    sleep 10
done

kill -INT $pid || true


  


  It should

  


  

  • put the second in the middle of the screen - 'cause it gets it from the source video

  


  • put the approximate sixth of minute in the lower left corner
(only approximate because of the sleep but close enough)

  


  • put the the wall clock time in the upper left corner

  


  


  and it works

  


  make clock.mpg
./experiment.sh 0
vlc superclock0.mp4


  


  shows something like this


  


  Now here is the interesting part

  


  If I run the script in four different terminals at the same time

  


  ./experiment.sh 1
./experiment.sh 2
./experiment.sh 3
./experiment.sh 4


  


  It can't keep up with the frame rate, and I see this in the output :

  


  frame= 1515 fps= 16 q=0.0 size=     768kB time=00:00:59.96 bitrate= 104.9k


  


  I was hoping the end result would all look ok when I watch it except with fewer frames, but the timestamps of the frames would make it all work as expected

  


  However...

  


  

  • The time in the middle, that is inherited from the source video, the seconds in the middle of the screen, stays in sync with VLC's clock.

  


  • the wall clock in the upper left seems play at 150% speed

  


  • the every ten seconds incrementor in the lower left seems to increment every 7 seconds

  


  • the video is only 1:25 long even though it was recording for at least 1:40 according to sleeps

  


  • the wall clock in the upper right hand corner makes it more than 1'40" and then counter in the lower left makes it to 10.

  


  


  

  


  Here are four states to compare

  


  |                  | Start    | 30" in   | end      |
|------------------+----------+----------|----------|
| Video Time       | 00:00    | 00:30    | 01:24    |
| Wall Clock Time  | 15:05:50 | 15:06:39 | 15:07:39 |
| sixth of minute  | 0        | 4        | 10       |
| seconds counter  | 0        | 30       | 24       |


  


  

  


  So you can see the vlc clock keeps pace with the original clock from the source movie.. even when it is only able to produce frames at 2/3 of the rate. However, the it is taking 50% long to get through the whole source movie I guess ?

  


  I am having trouble coming up with a theory that can explain exactly how this happens.

  


  Does anybody know how I can "correct" this ? (make it so that the movie is played at the same rate that it is recorded)

  


  I am thinking of using a lower frame rate and size as the input video.. but it would be nice to have something that will always work as expected, just with a lower frame rate, no matter how busy the processor is.