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• Efficient and Perfect way to extract frames from a large size video using python or ffmpeg according the timecode given

  5 avril 2020, par Yong En

  let's say I have a video from youtube with at least 600 MB. The video is used for annotation where I have the annotated information in another text file. The annotation file has the timecode in millisecond (SSSS.ss). What I am trying to do is going into the timecode on the video and getting out the frames within the this period (TWO timecodes). There are TWO approaches that I used with different tools, one is using openCV in python and FFmpeg in bash script :

  



  I would stick with few variables here,

  



  

  • fps = 25

  


  • timecode (after convert into second) = 333.44 to 334.00 take note that I am dealing with time period that might less than a second.

  


  



  openCV

  



  

  1. Using openCV in python, I read the video into frame by frame. Ends up with a numpy array.

  


  2. Using the fps from video, eg. fps = 25. I can estimate where does the frames that fall under this time period which give me what I want.

  


  3. Problem here is I will missed out some frames here due to the video fps is not really 25 as given by the video misinformation, it could 24.xx. Any solutions ?

  


  



  ffmpeg

  



  

  1. What I did, every time I want to get the frames, I run the script.

  


  2. Problem here is I need to read the video 100 times if I have 100 time periods. Any ways to overcome this ?

  


  



  Thanks for reading it.

  


• Read RTSP stream in Python

  15 avril 2020, par pooorman

  I want to read RTSP stream with low latency. I use this code read frames in 100ms 200ms.
But this command will failed sometimes when restart program. There are four subprocess that read stream, 3 are success and 1 is failed. Is my command wrong ?

  



  ffmpeg_cmd = ["ffmpeg", "-v", "debug", "-y",
                        "-skip_initial_bytes", "2000000",
                        "-c:v",  "h264",
                        "-vsync", "1",
                        "-flags", "low_delay",
                        "-fflags", "nobuffer",
                        "-analyzeduration", "100000",
                        "-max_delay", "100000",
                        "-reorder_queue_size", "10000",
                        "-rtsp_transport", "tcp",
                        "-i", "rtsp://xx:xx@ip/streaming/channels/101",
                        "-s", "1280x720",
                        "-preset", "ultrafast",
                        "-tune", "zerolatency",
                        "-f", "image2pipe",
                        "-pix_fmt", "rgb24",
                        "-vcodec", "rawvideo",
                        "-r", "25",
                        "-"]
ffmpeg = sp.Popen(ffmpeg_cmd, stdout=sp.PIPE, bufsize=1024)
x = ffmpeg.stdout.read(int(w*h*3))


  



  Error message :

  



  Codec AVOption preset (Configuration preset) specified for output file #0 (pipe:) has not been used for any stream. The most likely reason is either wrong type (e.g. a video option with no video streams) or that it is a private option of some encoder which was not actually used for any stream.
Codec AVOption tune (Tune the encoding to a specific scenario) specified for output file #0 (pipe:) has not been used for any stream. The most likely reason is either wrong type (e.g. a video option with no video streams) or that it is a private option of some encoder which was not actually used for any stream.
detected 48 logical cores
Past duration 0.914436 too large
[h264 @ 0x55a59a5b8500] nal_unit_type: 7(SPS), nal_ref_idc: 3
[h264 @ 0x55a59a5b8500] nal_unit_type: 8(PPS), nal_ref_idc: 3
Clipping frame in rate conversion by 0.339165
[h264 @ 0x55a59a5b8500] nal_unit_type: 1(Coded slice of a non-IDR picture), nal_ref_idc: 3
[h264 @ 0x55a59a5b8500] Format yuvj420p chosen by get_format().
[h264 @ 0x55a59a5b8500] Reinit context to 1920x1088, pix_fmt: yuvj420p
[h264 @ 0x55a59a5b8500] Frame num gap 6 4
[h264 @ 0x55e256eef5c0] nal_unit_type: 7(SPS), nal_ref_idc: 3
[h264 @ 0x55e256eef5c0] nal_unit_type: 8(PPS), nal_ref_idc: 3
[h264 @ 0x55e256eef5c0] nal_unit_type: 5(IDR), nal_ref_idc: 3
[h264 @ 0x5649ea893700] nal_unit_type: 1(Coded slice of a non-IDR picture), nal_ref_idc: 3
    Last message repeated 3 times
[rtsp @ 0x5626b5bd85c0] max_analyze_duration 100000 reached at 120000 microseconds st:0
[rtsp @ 0x5626b5bd85c0] decoding for stream 0 failed


  


• Convert webm to mp3 using python ?

  28 avril 2020, par Andy_ye

  Yes I know that this has been asked many many times, but the libraries on every single answer just ends up needing ffmepg.

  



  The problem with that is that the file size increases dramatically when I include ffmpeg to my project, and I just don't want that.

  



  I want to keep my project as lightweight as possible without needing to add 200 meabytes of data just for video to audio conversion which is just a very small part of the project.

  



  So is there any way to

  



  

  • 

    1. not use ffmpeg

    


  


  • 

    2. use another lightweight converter with a python wrapper

    


  


  • 

    3. just use the parts in ffmpeg where the webm to mp3 conversion is actually taking place