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• ffmpeg FPS information mismatch with the video

  8 décembre 2017, par Adorn

  I have a bunch of videos with some statistics of what is happening inside a video. One such piece of information is given in terms of time of the video in seconds up to one decimal point.

  To get the FPS of a video, I am using ffmpeg -i

  But when I manually compute one particular frame’s time using given FPS, it does not match.

  For example, ffmpeg outputs FPS = 30.

  I look at the video statistics, the frame at the 156.8 = 2.368 has to be
  4704'th frame. I open the video using ’skvideo’, read all the frames, and view the 4704'th frame. It is some frame around time 2.12 ?. I checked multiple such instances in multiple videos and this is a common behavior.

  I do not understand why this is so and how can I get around the problem ?

  As such I am not bounded by ffmpeg. Skvideo is being used to read the videos. I tried opencv, as of now it does not work with VideoCapture, and reinstalling it is costly for me time wise. But I guess ’opencv/skvideo’ should not matter, one can count the frames manually as well.

  So, in the solution, I am looking out for -

  1. Given timestamps of inside of a video, how can I find a frame of that particular time location ?

  2. In case someone might have already worked on this, this is related to THUMOS dataset. I am on Ubuntu 16.04

  EDIT_1

  Actually I can be more specific as it is a publicly available data. The time bounds are of an important activity. For example, in a video, when does basketball dunk occurs ? It is given in pairs - [start end]. Some videos have multiple activities, some have only one.

  Here is a sample video, and following are the activity times.

  [[  16.5, 20.8],
  
  [  26.6, 32.2],
  
  [  34.8, 42.1],
  
  [  47.8, 50.0],
  
  [  58.1, 62.9],
  
  [  65.6, 67.2],
  
  [  68.5, 74.0],
  
  [  76.4, 78.3],
  
  [  78.7, 79.8],
  
  [  80.8, 82.1],
  
  [  85.0, 87.3],
  
  [  90.1, 91.4],
  
  [  98.5, 100.3]]

  I also tried checking manually, 32.87 FPS "almost" works for few videos but not for all. and almost means it is off by 10 frames. This is a huge difference for my task, and I need exact frame.

  Also, there has to be some way, because it can be visually observed with multiple video players that times in the dataset are correct.

• Get video duration of file hosted on Amazon S3

  10 janvier 2020, par Michi

  I’m starting a portal which distributes videos. The idea is to upload the videos to Amazon S3 and gather the necessary data using PHP from my server. So far everything works fine... the only thing I could not manage to get is the duration of the video :-( Could anybody give me a hint on how to accomplish it ?

  Thanks,
  Miguel

  UPDATE :

  I finally opted to do it using FFmpeg. I have already installed FFmpeg on the server and I’m now trying to execute the command in the shell prior to execute it with PHP. I’m passing it the URL from Amazon (I tried both the cloudfront URL and the S3 URL) but it says that there is not such a directory or file. I’ve seen examples on the web using external files so I expected it to work.

  The command I’m using is

  ffmpeg -i https://s3-eu-west-1.amazonaws.com/path/to/file.m4v

  Is there something I need to configure in order to use external URLs ?

• Trying to tonemap 14-bit grayscale video

  12 janvier 2018, par Trevor

  I’m trying to generate h.264 video from raw 2-byte gray video (14-bit range encoded in 16-bit values). I can do something like :

  ffmpeg -f rawvideo -pix_fmt gray16le -s:v 1280x720 -r 60 -i input.raw -c:v libx264 output.mp4

  And I get video but it’s pretty dark, not sure if it’s clipping, doing a linear remap, or storing the 16-bit data and VLC is doing the remap. ffprobe is reporting Video: h264 (High 4:4:4 Predictive) (avc1 / 0x31637661), yuvj444p(pc), 1280x720, 108 kb/s, 60 fps, 60 tbr, 15360 tbn, 120 tbc

  I was figuring I’d use the tonemap filter to make a better mapping. I added a filter before the output file with -vf.

  • tonemap=hable errors Impossible to convert between the formats supported by the filter 'graph 0 input from stream 0:0' and the filter 'auto_scaler_0'
  • zscale=transfer=linear,tonemap=hable errors Impossible to convert between the formats supported by the filter 'Parsed_tonemap_1' and the filter 'auto_scaler_1'
  • zscale=transfer=linear,tonemap=hable,zscale=transfer=bt709,format=yuvj444p errors code 3074: no path between colorspaces

  I’m not sure where to proceed from here...