a53545a374
The SSIM filter uses the pixel values without considering the color ranges. This is incorrect. Patch adds a warning so at least the user knows it. Let's see an example. (1) Let's get FR and LR versions of the same image. ``` $ ffmpeg -y -i /tmp/lena.490x490.ppm -vf scale="out_range=full" -pix_fmt yuv420p /tmp/lena.full.y4m $ xxd /tmp/lena.full.y4m |head 00000000: 5955 5634 4d50 4547 3220 5734 3930 2048 YUV4MPEG2 W490 H 00000010: 3439 3020 4632 353a 3120 4970 2041 303a 490 F25:1 Ip A0: 00000020: 3020 4334 3230 6a70 6567 2058 5953 4353 0 C420jpeg XYSCS 00000030: 533d 3432 304a 5045 4720 5843 4f4c 4f52 S=420JPEG XCOLOR 00000040: 5241 4e47 453d 4655 4c4c 0a46 5241 4d45 RANGE=FULL.FRAME 00000050: 0a72 7271 7070 706f 6f6e 6d6d 6c6d 6d6d .rrqpppoonmmlmmm 00000060: 6c6e 6e6d 6d6e 6e6e 6d6c 6d6d 6d6d 6d6d lnnmmnnnmlmmmmmm 00000070: 6d6e 6d6b 6c6d 6e6e 6d6c 6d6d 6e6e 6f6f mnmklmnnmlmmnnoo 00000080: 6f6f 6e6e 6e6e 6f70 7172 7375 7676 7370 oonnnnopqrsuvvsp 00000090: 6d69 6662 5e59 534d 4845 3d35 302e 2d2c mifb^YSMHE=50.-, ``` ``` $ ffmpeg -y -i /tmp/lena.490x490.ppm -vf scale="out_range=limited" -pix_fmt yuv420p /tmp/lena.limited.y4m $ xxd /tmp/lena.limited.y4m | head 00000000: 5955 5634 4d50 4547 3220 5734 3930 2048 YUV4MPEG2 W490 H 00000010: 3439 3020 4632 353a 3120 4970 2041 303a 490 F25:1 Ip A0: 00000020: 3020 4334 3230 6a70 6567 2058 5953 4353 0 C420jpeg XYSCS 00000030: 533d 3432 304a 5045 4720 5843 4f4c 4f52 S=420JPEG XCOLOR 00000040: 5241 4e47 453d 4c49 4d49 5445 440a 4652 RANGE=LIMITED.FR 00000050: 414d 450a 7272 7170 7070 6f6f 6e6e 6e6d AME.rrqpppoonnnm 00000060: 6e6e 6e6d 6f6e 6e6e 6e6e 6e6e 6d6e 6e6e nnnmonnnnnnnmnnn 00000070: 6e6e 6e6e 6f6e 6c6d 6e6f 6e6e 6d6e 6e6f nnnnonlmnonnmnno 00000080: 6f6f 6f6f 6f6f 6f6f 6f6f 7071 7273 7576 oooooooooopqrsuv 00000090: 7673 706e 6a68 6461 5c57 524e 4b44 3d39 vspnjhda\WRNKD=9 ``` Note that the 2x images are the same. Only difference is the range, and the precision issues related to range conversion. (2) Let's calculate the SSIM score: ``` $ ./ffmpeg -filter_threads 1 -filter_complex_threads 1 -i /tmp/lena.full.y4m -i /tmp/lena.limited.y4m -lavfi "ssim" -f null - ... [Parsed_ssim_0 @ 0x360ab00] SSIM Y:0.942347 (12.391801) U:0.995808 (23.776062) V:0.996104 (24.093747) All:0.960217 (14.003012) ``` As we are comparing an image with itself, we expect "Y: 1" as the luma SSIM. Issue here is that the SSIM filter just uses the pixel values, ignoring the color ranges. Proposed solution is to add a warning. ``` $ ./ffmpeg -filter_threads 1 -filter_complex_threads 1 -i /tmp/foo.full.y4m -i /tmp/foo.limited.y4m -lavfi "ssim" -f null - ... [Parsed_ssim_0 @ 0x3766280] master and reference frames use different color ranges (pc != tv) ... [Parsed_ssim_0 @ 0x3766280] SSIM Y:0.000000 (0.000000) U:0.000000 (0.000000) V:0.000000 (0.000000) All:0.000000 (0.000000) ``` Tested: Ran fate. ``` $ make fate -j ... TEST seek-lavf-ppmpipe TEST seek-lavf-pgmpipe TEST seek-lavf-mxf_opatom ```
FFmpeg README
FFmpeg is a collection of libraries and tools to process multimedia content such as audio, video, subtitles and related metadata.
Libraries
libavcodecprovides implementation of a wider range of codecs.libavformatimplements streaming protocols, container formats and basic I/O access.libavutilincludes hashers, decompressors and miscellaneous utility functions.libavfilterprovides means to alter decoded audio and video through a directed graph of connected filters.libavdeviceprovides an abstraction to access capture and playback devices.libswresampleimplements audio mixing and resampling routines.libswscaleimplements color conversion and scaling routines.
Tools
- ffmpeg is a command line toolbox to manipulate, convert and stream multimedia content.
- ffplay is a minimalistic multimedia player.
- ffprobe is a simple analysis tool to inspect multimedia content.
- Additional small tools such as
aviocat,ismindexandqt-faststart.
Documentation
The offline documentation is available in the doc/ directory.
The online documentation is available in the main website and in the wiki.
Examples
Coding examples are available in the doc/examples directory.
License
FFmpeg codebase is mainly LGPL-licensed with optional components licensed under GPL. Please refer to the LICENSE file for detailed information.
Contributing
Patches should be submitted to the ffmpeg-devel mailing list using
git format-patch or git send-email. Github pull requests should be
avoided because they are not part of our review process and will be ignored.