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• opencv cannot read MP4 file from sony camcorder

  7 juin 2016, par Jundong

  The sony camcorder recorded video in MP4 format. I am reading the file by

  import cv2
  
  vid = cv2.VideoCapture('sample.MP4')

  my OpenCV version is 2.4.8, as a Python module.

  The codec of the ’sample.MP4’ is H.264, Linear PCM.

  ffprobe sample.MP4

  returns :

  > Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'C0004.mp4':   Metadata:
  
  >     major_brand     : XAVC
  
  >     minor_version   : 16785407
  
  >     compatible_brands: XAVCmp42iso2
  
  >     creation_time   : 2016-06-06 13:41:51   Duration: 00:00:15.02, start: 0.000000, bitrate: 50439 kb/s
  
  >     Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709/bt709/iec61966-2-4), 1920x1080 [SAR 1:1 DAR 16:9],
  
  > 48655 kb/s, 29.97 fps, 29.97 tbr, 30k tbn, 59.94 tbc (default)
  
  >     Metadata:
  
  >       creation_time   : 2016-06-06 13:41:51
  
  >       handler_name    : Video Media Handler
  
  >       encoder         : AVC Coding
  
  >     Stream #0:1(und): Audio: pcm_s16be (twos / 0x736F7774), 48000 Hz, 2 channels, s16, 1536 kb/s (default)
  
  >     Metadata:
  
  >       creation_time   : 2016-06-06 13:41:51
  
  >       handler_name    : Sound Media Handler
  
  >     Stream #0:2(und): Data: none (rtmd / 0x646D7472), 245 kb/s (default)
  
  >     Metadata:
  
  >       creation_time   : 2016-06-06 13:41:51
  
  >       handler_name    : Timed Metadata Media Handler 
  
  > Unsupported codec with id 0 for input stream 2

  It seems that the codec for h.264 is missing. The version of my FFmpeg is 3.0.

  I tried avconv -i sample.MP4 -c:a copy -c:v copy sample_converted.mp4 to convert the sample.MP4 to sample_converted.mp4, this command line did not work. The command ffmpeg -i sample.mp4 sample_converted.mp4 worked ; however, it compromised the video quality badly.I used an online video converter : http://www.online-convert.com/ (which output nice quality video in mp4 format, but it has size limitation for free users)
  to convert the MP4 to mp4, the command in Terminal as below :

  ffprobe 'sample_converted.mp4'

  returns

  > Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'C0001_converted.mp4':  
  
  > Metadata:
  
  >     major_brand     : isom
  
  >     minor_version   : 512
  
  >     compatible_brands: isomiso2avc1mp41
  
  >     encoder         : Lavf57.36.100   Duration: 00:00:02.02, start: 0.000000, bitrate: 16777 kb/s
  
  >     Stream #0:0(und): Video: h264 (Constrained Baseline) (avc1 / 0x31637661), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], 16801 kb/s, 59.94
  
  > fps, 59.94 tbr, 60k tbn, 119.88 tbc (default)
  
  >     Metadata:
  
  >       handler_name    : VideoHandler
  
  >     Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 127 kb/s (default)
  
  >     Metadata:
  
  >       handler_name    : SoundHandler

  Obviously, the encoders, handler_names etc. of the sample.MP4 and sample_converted.mp4 are different. Any idea using FFmpeg or OpenCV to convert this raw video from camcorder to the readable format without compromising the video quality ?

• How can I make sure trimming in ffmpeg with -c:v copy is accurate

  9 avril 2020, par Angelo

  I looked at many things online and I understand it's better to re-encode if you want precision.

  



  But for instance, I have the following command :

  



  -ss 00:00:09 -i "input.mp4" -c:v copy -c:a copy -vframes 600 "output.mp4


  



  Where 600 is calculated using the video's FPS and duration, in this case 10 seconds from an 60FPS video. Can I expect to get something accurate with this all the time ? I tested many variants but this seems to be doing ok for the couple videos I tested for.. And if not, can I really ever get complete ACCURACY with copying, or must I stick to H264 for instance ?

  


• Android video encoding with fr and resolution manipulation

  24 février 2017, par apSTRK

  I want to be able to take a video recorded with an Android device and encode it to a new Resolution and Frame Rate using my app. The purpose is to upload a much smaller version of the original video (in size), since this will be videos 30 min long or more.

  So far, I’ve read of people saying FFmpeg is they way to go. However, the documentation seems to be lacking.

  I have also considered using http opencv http://opencv.org/platforms/android.html

  Considering I need to manipulate the video resolution and frame rate, which tool do you think can do such things better ? Are there any other technologies to consider ?

  An important question is, since this will be long videos, is it reasonable to do the encoding in an android device (Consider power resources, time, etc.)

  Thanks in advance !