The frame quantization and/or rounding frame rates calculations the “fps” filter does internally will end up outputting different frames than -r because the “fps” will not change the video length. The “fps” filter is meant to preserve the input length when converting between different frame rates. This is inevitable and what happens when -r is used to specify the frame rate. In constant frame rate video, only a certain number of frames are both allowed and required for a given length whenever frames are added or removed from the image sequence, there will be changes in video length as well. The frames in output.mkv using the “fps” filter will be different than using -r after -i and also different from the input. mkvįfmpeg will add or discard different frames depending on whether -r or video filter “fps” are in use. However, the algorithm of -r is different from video filter “fps.” ffmpeg -i "frames\f_%06d.png" -vf "fps=24" -c:v libx264 -crf 0 output. If the images were actually at 24 fps, then 25 fps would play the video faster (assuming a constant frame rate) and so it would be “shorter” than expected as well. Since ffmpeg had to drop frames to do a frame rate conversion, outpit.mkv would be missing frames. This is indeed frame rate conversion from 25 FPS to 24 FPS. The achievement of 24 FPS output, which is lower than the source input of 25 FPS, is only possible if some frames are dropped. Because -r is placed after -i the output video will be 24 FPS. Of course, omission of -r before -i in an image sequence means that ffmpeg will assume the source is at 25 FPS. But what if -r is placed after -i? ffmpeg -i "frames\f_%06d.png" -r 24 -c:v libx264 -crf 0 output. The conversion between discrete images and a video (lossless encoding) is thus reversible. Omission of -r in the output option (after -i) means the frame rate of the source should be used. ffmpeg can detect the frame rate from the source output.mkv. This case omits -r both before and after -i. The discrete images can be extracted back out of output.mkv: mkdir "frames"įfmpeg -i output.mkv "frames\f_ %06d.png" In that case: ffmpeg -r 24 -i "frames\f_%06d.png" -c:v libx264 -crf 0 output. The film industry generally chooses 24 FPS in film capturing and production. crf “0”, short for “constant rate factor,” is used to tell the libx264 encoder to use “lossless mode.” If placed after -i, then -r would indicate the output rate. Note that to tell ffmpeg the still images or input frame rate is 24 FPS, -r is placed before -i. It is 25 FPS because -r “25” is the default preset in ffmpeg for GOP input. Since one was not specified and there is no inherent frame rate for discrete images the framerate will be 25. Notice there was no frame rate specified. For example: ffmpeg -i "frames\f_%06d.png" -c:v libx264 -crf 0 output.
#Encode avisynth ffmpeg series#
r is not a replacement for video filter and vica-versa depending on usage scenarios.įfmpeg can encode a series of image sequence into a single video file. The “fps” video filter can handle frame rate conversion accurately with regards to not changing the length -r, on the other hand, is meant to assume a given frame rate and may change the video length. Q: What is the (technical) difference between -r and the “fps” filter?ĭisclaimer: The following is as well as I know and based on my (“thljcl’s”), and the blog’s author’s, own thoughts and experiments. Distribution codecs are not meant for editing, or storing the “master” image sequence. Videos meant for commercial release or distribution typically use highly compatible but lossy codecs. Lossy encoding in not a perfectly reversible process and doing it will compromise image quality, especially if done successively. In contrast to lossless, lossy encoding discards information present in the image sequence and so it is not possible to extract out the frames perfectly. Editing can include modifying, adding, removing, duplicating frames and treating them as “video clips.”
#Encode avisynth ffmpeg software#
We can edit “video” frame by frame as an image sequence in image manipulation programs ( Adobe Photoshop, mspaint, GIMP, ImageMagick, waifu2x), or in video editing software ( Adobe Premiere, AviSynth, Sony Vegas).
It is possible to decode that video file back to an image sequence for editing purposes and get back the original frames. Frame rates may be constant (CFR) or variable (VFR).Ī series of images in a sequence can be encoded into a single video file with lossless encoding (huffyuv, lagarith, x264 w/crf=0). Frame rate is the frequency at which an imaging device produces unique consecutive images called frames. Video Theory:īy definition, a video is a series of still images which, when shown on screen, creates the illusion of moving images.
The following is a heavily edited version of that post. Disclaimer: Most of following was originally written by thljcl and is available unedited at.
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