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• Grep for a number between a certain range - Checking WAV Quality

  11 août 2014, par BT643

  I’m trying to write a regular expression (to be used in conjunction with ffmpeg, which can check that a WAV file is over a certain quality.

  The minimum should be :

  Audio Channels : 2 (Stereo)
  Audio Sample Rate : 44,100 Hz
  Audio Bitrate : 1411 Kbps
  Audio Bit Depth : 16 bit
  

  So I’ve tried the following commands so far :

  • /usr/local/bin/ffmpeg -i "/path/to/file.wav" 2>&1 | egrep 'stereo|2 channels'

  This works fine to get a stero (2 channel) WAV. I’m getting issues with the next part, searching between a range of numbers.

  • /usr/local/bin/ffmpeg -i "/path/to/file.wav" 2>&1 | egrep 'stereo|2 channels' | egrep '[41000-196000] Hz'

  Obviously this just searches each number individually, so it’s finding results if there’s a 4 OR 1 OR 0 OR 0 OR 0 etc...

  The bit rate and bit depth just needs to be OVER 1411 and 16 respectively.

  Thanks

  EDIT -
  Here’s the ffmpeg output for a low quality WAV which should be rejected :

  ffmpeg version git-2012-05-22-27127eb Copyright (c) 2000-2012 the FFmpeg developers
 built on May 22 2012 12:27:21 with gcc 4.6.1
 configuration: --enable-gpl --enable-libfaac --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvorbis --enable-libx264 --enable-nonfree --enable-postproc --enable-version3 --enable-x11grab
 libavutil      51. 53.100 / 51. 53.100
 libavcodec     54. 21.101 / 54. 21.101
 libavformat    54.  6.100 / 54.  6.100
 libavdevice    53.  4.100 / 53.  4.100
 libavfilter     2. 75.100 /  2. 75.100
 libswscale      2.  1.100 /  2.  1.100
 libswresample   0. 15.100 /  0. 15.100
 libpostproc    52.  0.100 / 52.  0.100
[wav @ 0x355b140] max_analyze_duration 5000000 reached at 5056000
Guessed Channel Layout for  Input Stream #0.0 : stereo
Input #0, wav, from '/path/to/file.wav':
 Duration: 00:02:28.47, bitrate: 512 kb/s
   Stream #0:0: Audio: pcm_u8 ([1][0][0][0] / 0x0001), 32000 Hz, stereo, u8, 512 kb/s

• Basic "pass-through" use of FFmpegReader/FFmpegWriter in scikit-video

  6 février 2021, par JonathanZ supports MonicaC

  I am starting to use scikit-video and am having trouble writing files. I have reduced the problem to the simplest possible example

  


  vid_file = "6710185719062326259_stamp_25pct.mp4"
output_file = "out_temp3.mp4"
reader = skvideo.io.FFmpegReader(vid_file)
writer = skvideo.io.FFmpegWriter(output_file)
for frame in reader.nextFrame():
        writer.writeFrame(frame)
writer.close()


  


  I'm playing the files in VLC, and the vid_file is valid but the output file, though playable, is mostly big green blocks (though I can discern some details from the original video in it).

  


  My goal, or course, is to do "interesting" manipulations of the frame before I write it out, but I need to get the "no modifications" version working correctly first. I'm also going to be using this on large files, so the vread/vwrite functions that process an entire file at once are not appropriate.

  


  I'm guessing I need to set the appropriate values in the outputdict parameter for the FFmpegWriter, but there are so many that I don't know where to start. I have tried

  


  writer = skvideo.io.FFmpegWriter(output_file, outputdict={'-crf': '0', '-pix_fmt': 'rgb24'})


  


  (-crf 0 to suppress any compression, -pixfmt rgb24 as that's what FFmpegReader says it delivers by default, but these don't work either.

  


  Any ideas on how to make this work ?

  


  Here's the skvideo.io.ffprobe video information for the input file.

  


  {
    "@index": "0",
    "@codec_name": "h264",
    "@codec_long_name": "H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10",
    "@profile": "High",
    "@codec_type": "video",
    "@codec_time_base": "1/30",
    "@codec_tag_string": "avc1",
    "@codec_tag": "0x31637661",
    "@width": "480",
    "@height": "270",
    "@coded_width": "480",
    "@coded_height": "272",
    "@has_b_frames": "2",
    "@pix_fmt": "yuv420p",
    "@level": "21",
    "@chroma_location": "left",
    "@refs": "1",
    "@is_avc": "true",
    "@nal_length_size": "4",
    "@r_frame_rate": "15/1",
    "@avg_frame_rate": "15/1",
    "@time_base": "1/15360",
    "@start_pts": "0",
    "@start_time": "0.000000",
    "@duration_ts": "122880",
    "@duration": "8.000000",
    "@bit_rate": "183806",
    "@bits_per_raw_sample": "8",
    "@nb_frames": "120",
    "disposition": {
        "@default": "1",
        "@dub": "0",
        "@original": "0",
        "@comment": "0",
        "@lyrics": "0",
        "@karaoke": "0",
        "@forced": "0",
        "@hearing_impaired": "0",
        "@visual_impaired": "0",
        "@clean_effects": "0",
        "@attached_pic": "0",
        "@timed_thumbnails": "0"
    },
    "tag": [
        {
            "@key": "language",
            "@value": "und"
        },
        {
            "@key": "handler_name",
            "@value": "VideoHandler"
        }
    ]
}


  


  I will mention that when I ffprobe the output file the only differences I see are 1) the timing data is different, which isn't surprising, and 2) the output file has

  


      "@has_b_frames": "0",
    "@pix_fmt": "yuv444p",


  


  I'm pretty confident the reader is working okay, because if I write out the data with

  


  skimage.io.imsave('x.png', frame,  check_contrast=False)


  


  it looks good.

  


• avcodec/ac3enc : Use common encode_frame function

  7 avril 2024, par Andreas Rheinhardt

  avcodec/ac3enc : Use common encode_frame function
  This is in preparation for sharing even more stuff
  
  common to the fixed and floating-point encoders.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavcodec/ac3enc.c
  • [DH] libavcodec/ac3enc.h
  • [DH] libavcodec/ac3enc_fixed.c
  • [DH] libavcodec/ac3enc_float.c
  • [DH] libavcodec/ac3enc_template.c
  • [DH] libavcodec/eac3enc.c