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• ffmpeg (IMAGE THUMBNAIL 1 frame) how to "choose" compression quality when we use -vframes 1 (how to do like convert -quality 60....)

  25 juillet 2021, par jini

  • PRE-CONTEXT : with ImageMagick, I'm use to do convert -quality 60 1.jpg 1.webp here "quality 60" affect the final size of the output

  


  • CONTEXT : create a poster.webp OR poster.jpg of a movie.mp4

  


  • QUESTION : how can we "achieve" the same compression level choice with ffmpeg when we want 1 frame

  


  • WHAT I TRIED [1] :

  


  ffmpeg -i movie.mp4 -vframes 1 -qmin 0 -qmax 1  0.webp

  


  and ffmpeg -i movie.mp4 -vframes 1 -qmin 50 -qmax 51 50.webp

  


  ==>> both gives the exact same size for the output.

  


  • WHAT I TRIED [2] :

  


  ffmpeg -i movie.mp4 -vframes 1 -b:v 9k bv9k.webp

  


  and ffmpeg -i movie.mp4 -vframes 1 -b:v 1k bv1k.webp

  


  ==>> both gives the exact same size for the output.

  


  what I'm I missing or miss using here ?

  


  Thanks

  


• Why does x264 keep giving me "command not found" error on my Mac ? [closed]

  2 juillet 2021, par hd-dvd

  I just installed x264 via Homebrew on my Mac running MacOS 11.4 Big Sur. I'm trying to encode a video but I can't get x264 to run properly.

  


  This is the command I am running in the Terminal :

  


  x264 --bitrate 25000 --preset veryslow --bluray-compat --tune film --vbv-maxrate 40000 --vbv-bufsize 30000 --level 4.1 --keyint 30 --open-gop --slices 4 --fake-interlaced --colorprim "bt709" --transfer "bt709" --colormatrix "bt709" --sar 1:1 --pass 1 -o out.264 in.mp4

  


  and this is what it outputs :

  


  bash: x264 --bitrate 25000 --preset veryslow: command not found

  


  If I delete the --preset part then it just gets hung up on some other part, like --tune.

  


  I have tried brew doctor and there are no errors.

  


  If I just run x264 then it gives me x264 [error]: No input file. Run x264 --help for a list of options. so it seems as if x264 is installed. I don't know where to begin troubleshooting this but I'd like to get it to work.

  


  If I simplify the command way down to x264 -o out.264 in.mp4 then I get :

  


  avs [error]: failed to load avisynth
raw [error]: raw input requires a resolution.
x264 [error]: could not open input file `in.mp4' via any method!


  


  I would greatly appreciate some pointers on how to get this working.

  


• 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.