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• NumPy array of a video changes from the original after writing into the same video

  29 mars 2021, par Rashiq

  I have a video (test.mkv) that I have converted into a 4D NumPy array - (frame, height, width, color_channel). I have even managed to convert that array back into the same video (test_2.mkv) without altering anything. However, after reading this new, test_2.mkv, back into a new NumPy array, the array of the first video is different from the second video's array i.e. their hashes don't match and the numpy.array_equal() function returns false. I have tried using both python-ffmpeg and scikit-video but cannot get the arrays to match.

  


  Python-ffmpeg attempt :

  


  import ffmpeg
import numpy as np
import hashlib

file_name = 'test.mkv'

# Get video dimensions and framerate
probe = ffmpeg.probe(file_name)
video_stream = next((stream for stream in probe['streams'] if stream['codec_type'] == 'video'), None)
width = int(video_stream['width'])
height = int(video_stream['height'])
frame_rate = video_stream['avg_frame_rate']

# Read video into buffer
out, error = (
    ffmpeg
        .input(file_name, threads=120)
        .output("pipe:", format='rawvideo', pix_fmt='rgb24')
        .run(capture_stdout=True)
)

# Convert video buffer to array
video = (
    np
        .frombuffer(out, np.uint8)
        .reshape([-1, height, width, 3])
)

# Convert array to buffer
video_buffer = (
    np.ndarray
        .flatten(video)
        .tobytes()
)

# Write buffer back into a video
process = (
    ffmpeg
        .input('pipe:', format='rawvideo', s='{}x{}'.format(width, height))
        .output("test_2.mkv", r=frame_rate)
        .overwrite_output()
        .run_async(pipe_stdin=True)
)
process.communicate(input=video_buffer)

# Read the newly written video
out_2, error = (
    ffmpeg
        .input("test_2.mkv", threads=40)
        .output("pipe:", format='rawvideo', pix_fmt='rgb24')
        .run(capture_stdout=True)
)

# Convert new video into array
video_2 = (
    np
        .frombuffer(out_2, np.uint8)
        .reshape([-1, height, width, 3])
)

# Video dimesions change
print(f'{video.shape} vs {video_2.shape}') # (844, 1080, 608, 3) vs (2025, 1080, 608, 3)
print(f'{np.array_equal(video, video_2)}') # False

# Hashes don't match
print(hashlib.sha256(bytes(video_2)).digest()) # b'\x88\x00\xc8\x0ed\x84!\x01\x9e\x08 \xd0U\x9a(\x02\x0b-\xeeA\xecU\xf7\xad0xa\x9e\\\xbck\xc3'
print(hashlib.sha256(bytes(video)).digest()) # b'\x9d\xc1\x07xh\x1b\x04I\xed\x906\xe57\xba\xf3\xf1k\x08\xfa\xf1\xfaM\x9a\xcf\xa9\t8\xf0\xc9\t\xa9\xb7'


  


  Scikit-video attempt :

  


  import skvideo.io as sk
import numpy as np

video_data = sk.vread('test.mkv')

sk.vwrite('test_2_ski.mkv', video_data)

video_data_2 = sk.vread('test_2_ski.mkv')

# Dimensions match but...
print(video_data.shape) # (844, 1080, 608, 3)
print(video_data_2.shape) # (844, 1080, 608, 3)

# ...array elements don't
print(np.array_equal(video_data, video_data_2)) # False

# Hashes don't match either
print(hashlib.sha256(bytes(video_2)).digest()) # b'\x8b?]\x8epD:\xd9B\x14\xc7\xba\xect\x15G\xfaRP\xde\xad&EC\x15\xc3\x07\n{a[\x80'
print(hashlib.sha256(bytes(video)).digest()) # b'\x9d\xc1\x07xh\x1b\x04I\xed\x906\xe57\xba\xf3\xf1k\x08\xfa\xf1\xfaM\x9a\xcf\xa9\t8\xf0\xc9\t\xa9\xb7'


  


  I don't understand where I'm going wrong and both the respective documentations do not highlight how to do this particular task. Any help is appreciated. Thank you.

  


• FFmpeg IF/ELSE statement

  13 mai 2022, par Hrvoje

  I am doing reencoding of lots of video files, and sometimes some of them have subtitles included, some dont. Is it possible to "ignore"
-vf "subtitles=%%f:force_style='MarginV=25,Fontsize=20'" -sn statement in FFmpeg command IF input file does not have subtitles included ?

  


  My command is :

  


  for %%f in (*.mkv) do ffmpeg -hwaccel nvdec -i "%%f" -strict -2 -max_muxing_queue_size 1024 -map_metadata -1 -map_chapters -1 -vf "subtitles=%%f:force_style='MarginV=25,Fontsize=20'" -sn -c:v hevc_nvenc -rc vbr -cq 24 -qmin 24 -qmax 24 -tier high -level 4 -preset medium -profile:v main10 -pix_fmt p010le -b:v 0K -ac 6 -ar 48000 -b:a:0 640k -c:a:0 ac3 -metadata:s:a:0 title="Dolby Digital" E:\Encoded\%%f


  


  Note that there are more than 100 files in a batch and checking them by hand is time consuming.

  


  Maybe right aproach is to first inspect file in a batch script and if that file has subtitles, then execute first command, if it does not have subtitles, execute second command. But, I dont know how to do a script like that.

  


• 1 FPS slideshow with ffmpeg, produces 25 FPS anyway

  1er mai 2021, par ArekBulski

  I worked this command from other SO question :

  


  $ ffmpeg -i obraz%04d.png -framerate 1 -c:v libx265 output.mkv


  


  I tell it to make it 1 FPS at most, and yet both logs and Nautilus tell me the video is 25 FPS.

  


  Please suggest a course of action ?

  


  Full logs from ffmpeg :

  


  $ ffmpeg -i obraz%04d.png -framerate 1 -c:v libx265 output.mkv
ffmpeg version 4.3.1-4ubuntu1 Copyright (c) 2000-2020 the FFmpeg developers
  built with gcc 10 (Ubuntu 10.2.0-9ubuntu2)
  configuration: --prefix=/usr --extra-version=4ubuntu1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --enable-avresample --disable-filter=resample --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libdav1d --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librabbitmq --enable-librsvg --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opencl --enable-opengl --enable-sdl2 --enable-pocketsphinx --enable-libmfx --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-nvenc --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
  libavutil      56. 51.100 / 56. 51.100
  libavcodec     58. 91.100 / 58. 91.100
  libavformat    58. 45.100 / 58. 45.100
  libavdevice    58. 10.100 / 58. 10.100
  libavfilter     7. 85.100 /  7. 85.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  7.100 /  5.  7.100
  libswresample   3.  7.100 /  3.  7.100
  libpostproc    55.  7.100 / 55.  7.100
Input #0, image2, from 'obraz%04d.png':
  **Duration: 00:00:00.16,** start: 0.000000, bitrate: N/A
    Stream #0:0: Video: png, rgba(pc), 1848x1053, **25 fps**, 25 tbr, 25 tbn, 25 tbc
Stream mapping:
  Stream #0:0 -> #0:0 (png (native) -> hevc (libx265))
Press [q] to stop, [?] for help
x265 [info]: HEVC encoder version 3.4
x265 [info]: build info [Linux][GCC 9.3.0][64 bit] 8bit+10bit+12bit
x265 [info]: using cpu capabilities: MMX2 SSE2Fast LZCNT SSSE3 SSE4.2 AVX XOP FMA4 FMA3 BMI1
x265 [warning]: halving the quality when psy-rd is enabled for 444 input. Setting cbQpOffset = 6 and crQpOffset = 6
x265 [info]: Main 4:4:4 profile, Level-4 (Main tier)
x265 [info]: Thread pool created using 8 threads
x265 [info]: Slices                              : 1
x265 [info]: frame threads / pool features       : 3 / wpp(17 rows)
x265 [info]: Coding QT: max CU size, min CU size : 64 / 8
x265 [info]: Residual QT: max TU size, max depth : 32 / 1 inter / 1 intra
x265 [info]: ME / range / subpel / merge         : hex / 57 / 2 / 3
x265 [info]: Keyframe min / max / scenecut / bias  : 25 / 250 / 40 / 5.00 
x265 [info]: Cb/Cr QP Offset                     : 6 / 6
x265 [info]: Lookahead / bframes / badapt        : 20 / 4 / 2
x265 [info]: b-pyramid / weightp / weightb       : 1 / 1 / 0
x265 [info]: References / ref-limit  cu / depth  : 3 / off / on
x265 [info]: AQ: mode / str / qg-size / cu-tree  : 2 / 1.0 / 32 / 1
x265 [info]: Rate Control / qCompress            : CRF-28.0 / 0.60
x265 [info]: tools: rd=3 psy-rd=2.00 early-skip rskip mode=1 signhide tmvp
x265 [info]: tools: b-intra strong-intra-smoothing lslices=6 deblock sao
Output #0, matroska, to 'output.mkv':
  Metadata:
    encoder         : Lavf58.45.100
    Stream #0:0: Video: hevc (libx265), gbrp, 1848x1053, q=-1--1, 25 fps, 1k tbn, 25 tbc
    Metadata:
      encoder         : Lavc58.91.100 libx265
    Side data:
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: N/A
frame=    4 fps=0.0 q=35.9 Lsize=     137kB time=00:00:00.04 bitrate=27360.6kbits/s speed=0.0532x    
video:134kB audio:0kB subtitle:0kB other streams:0kB global headers:2kB muxing overhead: 2.194414%
x265 [info]: frame I:      1, Avg QP:30.46  kb/s: 27274.00
x265 [info]: frame P:      1, Avg QP:32.75  kb/s: 106.00  
x265 [info]: frame B:      2, Avg QP:35.38  kb/s: 29.60   
x265 [info]: Weighted P-Frames: Y:0.0% UV:0.0%
x265 [info]: consecutive B-frames: 50.0% 0.0% 50.0% 0.0% 0.0% 

encoded 4 frames in 0.71s (5.60 fps), 6859.80 kb/s, Avg QP:33.49