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• ffmpeg unique frames only

  5 novembre 2013, par William

  I have a video sequence (MPEG1) of 30 fps that is decoded in two ways :

  • opencv_ffmpeg returns 30 images per second, but only 5 of them are unique, while all others are clones of the unique ones.

  • proprietary players (MediaPlayer) returns only the 5 unique frames and "holds" them for (1/5) sec each.

  Is there a way to grab only the unique frames that the coder knows and not the total amount the ffmpeg decoder produces to fulfill the fps rate ?

  I'm developing a tracker and my tracker is forced to run 6 times slower and do many mistakes due to these "cloned frames".

  Does anyone know any technical term to the problem ? Unfortunately, ffmpeg is a black box for an opencv user and the documentation is sparse.

• iOS video streaming to server using websockets

  6 septembre 2013, par user1516711

  Is it any way possible to stream video frames live from iOS SDK using AVCaptureSession to a remote server using WebSocket like SocketRocket ? What are pros and cons if it is possible ?

• ffmpeg extract segment from video on-the-fly

  29 novembre 2022, par brunoais

  Context

  


  I want to make a service that hosts mp4 files but also provides video streaming.

  


  The server side is made of 2 "small" edge servers with capacity to cache about 0.1% of the content and one main server with a fraction of the bandwidth of the edge servers but much more robust storage.

  


  Recent status

  


  With the help of the ffmpeg manual,
  
Recently, when a segment is requested by an edge server, I run this command in ffmpeg

  


  ffmpeg -i in.mp4 -f hls -hls_list_size 0 -hls_playlist 1 -hls_time 60 -strftime 1  -hls_flags independent_segments+second_level_segment_index+second_level_segment_duration -hls_base_url '/path/to/file/' -hls_segment_filename 'name_%%03d.ts'  -c copy -copyts -hls_segment_type fmp4 out.m3u8


  


  Then obtain the requested segment (plus 3 subsequent ones) then delete everything.

  


  Current status

  


  Currently, I tried to get some level of optimization using -to :

  


  ffmpeg -i in.mp4 -to  -f hls -hls_list_size 0 -hls_playlist 1 -hls_time 60 -strftime 1  -hls_flags independent_segments+second_level_segment_index+second_level_segment_duration -hls_base_url '/path/to/file/' -hls_segment_filename 'name_%%03d.ts'  -c copy -copyts -hls_segment_type fmp4 out.m3u8


  


  Then sending the requested segments to the edge that requested them, then delete the result.
Do note that /path/to/file/ is a tmpfs with quite modest capacity (files can't stay there for too long).

  


  The current setback

  


  The main issue I get with the current process is that it takes a long time to obtain the last segments (2-4s).
That creates a bottleneck in how long segments take to be served. I can increase the buffer from 3 videos to 5 (or even more) but that doesn't solve the actual problem and, instead, will bring more strain on other areas.

  


  Cutting is not reliable

  


  There doesn't seem to exist an option to select what segments to generate using ffmpeg.

  


  Using cutting argument for start time (-ss) has shown to usually work but regularely causes the first keyframe used to be wrong. However, I believe I have all segment files in variable length and cut at the keyframe of the original file.

  


  Help needed

  


  How to extract an arbitrary segment of an mp4, described in the m3u8 file (which was done in a previous extraction) ?

  


  I have full control over ffmpeg and I can automate edits to the m3u8 file after generating them, as required. However, I need to understand and see how can this be solved.