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• How to convert MPEG2-TTS to MPEG2-TS format to playback using ffplay

  29 février 2024, par Asustor

  I know some OSS such as ffmpeg or gstreamer don't support to play-back MPEG2-TTS stream.
Then, I tried to convert 192 bytes TTS packet to 188 bytes TS packet by deleting first 4 bytes like :

  


  def conv_tts2ts(rtp_payload):

    payload_len = len(rtp_payload)
    if payload_len % 192 != 0:
        raise

    pkt_num = int(payload_len / 192)
    ts_data = bytearray()
    for i in range(pkt_num):
        spos = 192 * i
        epos = spos + 192
        tmp = rtp_payload[spos:epos]
        ts_data.extend(tmp[4:])

    return ts_data

# after this, send ts_data with RTP header received from MPEG2-TTS streamer via UDP/IP.



  


  However, ffplay and ffprobe don't reaction.

  


  I expect to be able to play-back using ffplay as MPEG2-TS format.
Please tell me how to convert TTS to TS in order to deocde by ffmpeg ?

  


• ffmpeg setting chapters by framecount instead of milliseconds ?

  28 septembre 2022, par BabaG

  I've just gone through a process of adding chapters to a file using ffmpeg. Works great but, the way I found to do it required converting the marker placements to milliseconds from the original timecode. Since my editing software will display my files with framecounts, it occurred to me that it might be possible to save some conversion effort by telling ffmpeg where to place the chapter markers using these framecounts.

  


  Here's an example of a chapter marker I placed :

  


  [CHAPTER]
TIMEBASE=1/1000
START=7000
END=291199
title=Chapter marker


  


  I see that the TIMEBASE is set to 1/1000. That means that the START time for this chapter is 7 seconds (210 frames). To what extent will ffmpeg accept a formula as its TIMEBASE ? Can I put in something like :

  


  [CHAPTER]
TIMEBASE=1/30
START=210
END=8736
title=Chapter marker


  


  or

  


  [CHAPTER]
TIMEBASE=100/2997
START=210
END=8736
title=Chapter marker


  


  thanks.

  


• Converting limited range YUV to sRGB using ImageMagick

  6 juillet 2019, par Rotem

  I am trying to convert a set of raw video frames from YUV444 to sRGB using ImageMagick.

  Input format : Raw YUV444 limited range, BT.709 in planar data order.
  Required output format : sRGB (set of PNG images).

  Main issue : ImageMagick conversion always applies JPEG conversion formula.

  • Remark about "limited range" YUV format :
    In 8 bits limited range YUV format, the range of Y is [16, 235] and the range of U, V is [16, 240]. (limited range BT.709 is used in HTDV systems).
    JPEG uses "full range" YUV format, where Y,U,V range is [0, 255].
    sRGB is used in PC systems, and the range of R,G,B is full range [0, 255].
    YUV and YCbCr are interchangeable.

  For testing, I used the following sample image :

  • Sample image in sRGB format (rgb_input.png) :
    

  I converted the sample to YUV444 format using FFmpeg :
  ffmpeg -y -colorspace bt709 -i rgb_input.png -pix_fmt yuv444p yuv_input.yuv

  Following image illustrates the YUV444 output (in planar data order) :

  • Input image for ImageMagick in YUV444 format (yuv_input.yuv planar data order illustration) :
    

  I converted yuv_input.yuv to PNG using ImageMagick converter (version 7.0.8-51) :
  magick -depth 8 -interlace plane -size 128x96 -colorspace Rec709YCbCr -sampling-factor 4:4:4 yuv:yuv_input.yuv rgb_output_magick.png

  • Result of ImageMagick (rgb_output_magick.png) :
    
    If you look carefully you see that the image is different than rgb_input.png.

  Same conversion using FFmpeg (used as reference) :
  ffmpeg -y -s 128x96 -colorspace bt709 -pix_fmt yuv444p -i yuv_input.yuv -pix_fmt rgb24 rgb_output_ffmpeg.png

  • Result of FFmpeg (rgb_output_ffmpeg.png) :
    
    Note : The true format of my raw input video frames prevents me from using FFmpeg.

  Conversion formula from 8 bits limited range YUV BT.709 to sRGB :
  R = 1.1644*Y + 0.00000*U + 1.79270*V - 248.10
G = 1.1644*Y - 0.21325*U - 0.53291*V + 76.878
B = 1.1644*Y + 2.11240*U + 0.00000*V - 289.02

  How can I do the above conversion using ImageMagick converter ?