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Chema Gonzalez a53545a374 lavfi/vf_ssim: add warning when color ranges differ 
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
```
2023-09-23 15:55:47 +01:00
compat configure: Set WIN32_LEAN_AND_MEAN at configure time 2023-08-14 22:57:28 +03:00
doc lavc/vaapi_encode: Add VAAPI AV1 encoder 2023-09-22 13:15:00 +08:00
ffbuild configure: probe RISC-V Vector extension 2022-09-27 13:19:52 +02:00
fftools fftools/ffmpeg: deprecate the -top option 2023-09-18 17:16:06 +02:00
libavcodec avcodec/flicvideo: fix decoding with AVFrame's negative linesize 2023-09-23 15:31:44 +02:00
libavdevice avdevice/android_camera: fix missing include for usleep 2023-09-19 00:39:47 +08:00
libavfilter lavfi/vf_ssim: add warning when color ranges differ 2023-09-23 15:55:47 +01:00
libavformat avformat/mov: Avoid cloning encryption info if its unchanged 2023-09-22 23:47:39 +02:00
libavutil avutil/avutil: make AV_TIME_BASE_Q available in C++ 2023-09-19 00:52:21 +08:00
libpostproc version.h: Bump minor post 6.0 branch 2023-02-19 18:37:36 +01:00
libswresample libswresample: Prevent out of bounds. 2023-08-02 17:31:13 +02:00
libswscale avutil/internal: Don't auto-include emms.h 2023-09-04 11:04:45 +02:00
presets
tests lavc/av1: Add unit test for level handling 2023-09-22 13:15:01 +08:00
tools tools/target_dec_fuzzer: Adjust threshold for rtv1 2023-09-22 23:47:40 +02:00
.gitattributes fate: add SCC test 2017-01-27 17:06:42 +01:00
.gitignore gitignore: add config_components.h 2022-03-17 18:35:41 -03:00
.mailmap mailmap: stop git lying about who I commit things as 2022-11-04 19:37:46 +01:00
.travis.yml Merge commit '899ee03088d55152a48830df0899887f055da1de' 2019-03-14 15:53:16 -03:00
Changelog lavc/vaapi_encode: Add VAAPI AV1 encoder 2023-09-22 13:15:00 +08:00
configure lavc/vaapi_encode: Add VAAPI AV1 encoder 2023-09-22 13:15:00 +08:00
CONTRIBUTING.md Add CONTRIBUTING.md 2016-09-18 10:02:13 +01:00
COPYING.GPLv2
COPYING.GPLv3
COPYING.LGPLv2.1
COPYING.LGPLv3
CREDITS Use https for repository links 2023-03-01 21:59:10 +01:00
INSTALL.md INSTALL.md: Fix Markdown formatting 2019-01-31 10:29:16 -09:00
LICENSE.md avfilter/vf_geq: Relicense to LGPL 2019-12-28 11:20:48 +01:00
MAINTAINERS MAINTAINERS: change Leo Izen IRC nickname 2023-06-20 12:46:47 -04:00
Makefile tools: add an AV_CODEC_CAP_ENCODER_RECON_FRAME test tool 2023-03-28 13:00:42 +02:00
README.md README: fix typo and description of libavfilter 2021-10-08 09:44:34 +05:30
RELEASE RELEASE: update after 5.1 branch 2022-07-13 00:31:42 +02:00

README.md

FFmpeg README

FFmpeg is a collection of libraries and tools to process multimedia content such as audio, video, subtitles and related metadata.

Libraries

  • libavcodec provides implementation of a wider range of codecs.
  • libavformat implements streaming protocols, container formats and basic I/O access.
  • libavutil includes hashers, decompressors and miscellaneous utility functions.
  • libavfilter provides means to alter decoded audio and video through a directed graph of connected filters.
  • libavdevice provides an abstraction to access capture and playback devices.
  • libswresample implements audio mixing and resampling routines.
  • libswscale implements 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, ismindex and qt-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.