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• FFmpeg cannot extract correct first frame - always extract the second frame [closed]

  21 octobre 2024, par Cai Yu

  I am on macos Ventura 13.2.1, on Macbook Pro M1Max.

  


  The video is number counting animation video. From 2 to 125. The number on first frame is 2. The number on last frame is 125. The number plus one on each frame. You can download the video here.

  


  NOTE that :
First, you hit space bar to play it in Finder, you can see the first frame of the video is number 2.

  


  Second, in professional Video editing software - davinci resolve, on the timeline, you can see the first frame is number 2.

  


  Now I try to use FFmpeg to extract the first frame of the video.
First Try :

  


  ffmpeg -i /Users/chris/Downloads/2to125.mov -vframes 1 /Users/chris/Downloads/1.png


  


  The output png image is number 3. So it's actually the second frame.

  


  Second try :

  


  ffmpeg -i /Users/chris/Downloads/2to125.mov -frames:v 1 /Users/chris/Downloads/1.png


  


  The output png image is still the second frame - the number 3.

  


  Third try :

  


  ffmpeg -i /Users/chris/Downloads/2to125.mov -vf "select=eq(n\,0)" -q:v 3 /Users/chris/Downloads/1.png


  


  The output image is sitll the wrong second frame.

  


  NOTE that :

  


  first : all these three method are from internet. And a lot of people voted correct answer for this question.

  


  second : all their output on my system is the incorrect second frame, not the first frame.

  


  I cannot find what's wrong. Hope friend here help me.

  


• ffmpeg not adding correct timestamps in recorded files [closed]

  27 avril 2023, par Aman Hanjra

  I am using ffmpeg to record a camera stream using rtsp protocol. I am creating 10 second files by setting output_ts_offset to epoch realtime.
ffmpeg command :
ffmpeg -hide_banner -loglevel warning -rtsp_transport tcp -i rtsp://camera_ip:camera_port/stream_url -muxpreload 0 -muxdelay 0 -c:v copy -an -f segment -strftime 1 -segment_time 10 -output_ts_offset $EPOCHREALTIME -segment_atclocktime 1 -segment_clocktime_offset 30 -segment_format mp4 file_%s_10.mp4

  


  Each file is saved with offset - start_time as epoch timestamp(current timestamp when ffmpeg pipeline starts and keep on adding 10 seconds as it creates 10 second files) and adding the same timestamp in file name also. eg file_1669903600_10.mp4
FPS is 15.
ffprobe output :

  


  start_time=1669903599.93233
duration=10.106771
[/STREAM]
[FORMAT]
filename=file_1669903600_10.mp4
[/FORMAT]

[STREAM]
start_time=**1669903605.53452**
duration=10.106771
[/STREAM]
[FORMAT]
filename=file_**1669903610**_10.mp4
[/FORMAT]


  


  In second example, there is difference of 5 seconds in start_time and filename which is incorrect.
Similarily sometimes there are differences upto 50000 seconds in timestamps.

  


  Files are being saved with start_time metadata either in past or future. Anyone faced the same issue with ffmpeg ?

  


  Sometimes I am getting files with 76ms duration and then this timestamp diff(start_time - filename timestamp) starts increasing negatively by 10 and goes up to -47270(in past) or sometimes it goes in future.

  


  Tried fixing the fps to 15(-r 15 argument) but didn't work.

  


  Expected output :
Timestamps should match(start_time timestamp should be equal to filename timestamp)

  


• What would be the correct way to use Exec or Transcode ffmpeg in SRS version of Windows 5.0.128

  29 janvier 2023, par diegosn79

  i was doing tests in different ways, and i can't use the Exec or Transcode option, i highlight that I have copied the ffmpeg.exe in the objs folder.
These are the codes I tried, and I attach the log errors.

  


  exec {

enabled on;

publish ./objs/ffmpeg.exe -rtbufsize 10M -i rtmp://10.1.9.240/live/encoder  -vf scale=1080:720 -c:v libx264 -profile:v high -level 4.2 -preset fast -b:v 1500k -c:a aac -ac 2 -b:a 96k -f flv -y rtmp://10.1.9.240:1935/live/encoderlow/;

}


  


  LOGS

  


  [2023-01-04 10:05:46.410][WARN][1309][01568ctu][11] EXEC : Ignore error, code=3028(FFmpegFork)(Failed to fork FFmpeg trancoder process) :
process start : vfork process failed, cli=./objs/ffmpeg.exe -rtbufsize 10M -i rtmp ://10.1.9.240/live/encoder -vf scale=1080:720 -c:v libx264 -profile:v high -level 4.2 -preset fast -b:v 1500k -c:a aac -ac 2 -b:a 96k -f flv -y rtmp ://10.1.9.240:1935/live/encoderlow/
thread [1309][01568ctu] : do_cycle() [./src/app/srs_app_ng_exec.cpp:108][errno=11]
thread [1309][01568ctu] : start() [./src/app/srs_app_process.cpp:197][errno=11]

  


  transcode

  


      enabled     on;

    ffmpeg      ./objs/ffmpeg.exe;

    engine ff {

        enabled         on;

        vfilter {

        }

        vcodec          libx264;

        vthreads        4;

        vprofile        high;

        vpreset         fast;

        vbitrate        1500k;

        vparams {

        }

        acodec          libfdk_aac;

        aparams {

        }

        output          rtmp://127.0.0.1:[port]/[app]/[stream]_[engine]?vhost=[vhost];

    }

}


  


  LOGS

  


  [2023-01-04 11:04:45.295][WARN][1489][34r32764][11] Encoder : Ignore error, code=3028(FFmpegFork)(Failed to fork FFmpeg trancoder process) : ffmpeg start : vfork process failed, cli=./objs/ffmpeg.exe -f flv -i rtmp ://127.0.0.1:1935/live ?vhost=defaultVhost/encoder -vcodec libx264 -b:v 1500000 -threads 4 -profile:v high -preset fast -acodec libfdk_aac -f flv -y rtmp ://127.0.0.1:1935/live/encoder_ff ?vhost=defaultVhost 1 > ./objs/ffmpeg-encoder-defaultVhost-live-encoder-ff.log 2 > ./objs/ffmpeg-encoder-defaultVhost-live-encoder-ff.log
thread [1489][34r32764] : do_cycle() [./src/app/srs_app_encoder.cpp:117][errno=11]
thread [1489][34r32764] : start() [./src/app/srs_app_process.cpp:197][errno=11]