photocd file fails to decode

[ami_stuff]

​https://telparia.com/fileFormatSamples/image/pcd/maddog.pcd

./ffmpeg -i maddog.pcd -y out.jpg
ffmpeg version N-112164-gcb26b85953 Copyright (c) 2000-2023 the FFmpeg developers
  built with gcc 11 (Ubuntu 11.4.0-1ubuntu1~22.04)
  configuration: 
  libavutil      58. 25.100 / 58. 25.100
  libavcodec     60. 27.100 / 60. 27.100
  libavformat    60. 13.100 / 60. 13.100
  libavdevice    60.  2.101 / 60.  2.101
  libavfilter     9. 11.100 /  9. 11.100
  libswscale      7.  3.100 /  7.  3.100
  libswresample   4. 11.100 /  4. 11.100
Input #0, image2, from 'maddog.pcd':
  Duration: 00:00:00.04, start: 0.000000, bitrate: 867942 kb/s
  Stream #0:0: Video: photocd, yuv420p(pc, bt709/bt709/iec61966-2-1), 3072x2048, 25 fps, 25 tbr, 25 tbn
Stream mapping:
  Stream #0:0 -> #0:0 (photocd (native) -> mjpeg (native))
Press [q] to stop, [?] for help
[vist#0:0/photocd @ 0x55c65327b900] Decoding error: Invalid data found when processing input
[swscaler @ 0x55c6532b5140] deprecated pixel format used, make sure you did set range correctly
[vost#0:0/mjpeg @ 0x55c653280380] No filtered frames for output stream, trying to initialize anyway.
[vost#0:0/mjpeg @ 0x55c653280380] No information about the input framerate is available. Falling back to a default value of 25fps. Use the -r option if you want a different framerate.
Output #0, image2, to 'out.jpg':
  Metadata:
    encoder         : Lavf60.13.100
  Stream #0:0: Video: mjpeg, yuvj420p(pc, progressive), 3072x2048, q=2-31, 200 kb/s, 25 fps, 25 tbn
    Metadata:
      encoder         : Lavc60.27.100 mjpeg
    Side data:
      cpb: bitrate max/min/avg: 0/0/200000 buffer size: 0 vbv_delay: N/A
[vist#0:0/photocd @ 0x55c65327b900] Decode error rate 1 exceeds maximum 0.666667
[out#0/image2 @ 0x55c65327be80] video:0kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
[out#0/image2 @ 0x55c65327be80] Output file is empty, nothing was encoded(check -ss / -t / -frames parameters if used)
frame=    0 fps=0.0 q=0.0 Lsize=N/A time=N/A bitrate=N/A speed=N/A    
Conversion failed!

[Elon Musk]

And what software decodes it?

[ami_stuff]

this tool for example:

​https://sourceforge.net/projects/pcdtojpeg/

[Balling]

Yep. Other pcd files work great (except for color management, but whatever).

[Elon Musk]

Here it decodes always same colors.

[Balling]

Replying to Elon Musk:

Here it decodes always same colors.

Which are wrong colors. I told you years ago it uses xvYCC, not sRGB transfer. It is like you cannot read the English language.

​https://en.wikipedia.org/wiki/XvYCC

[Elon Musk]

MPV displays correct colors, better one then that app that converts it to rgb ppm.

FFplay does not support most of colorspace stuff.

[Balling]

MPV displays correct colors

No. You need PQ to correctly show the colors, as the content is HDR and WCG (both outside 100 nits and BT.709 primaries).

​https://github.com/FFmpeg/FFmpeg/blob/8eb094adb2ac3b6ea1d2cdd0fdfc7b69b2084db9/libavcodec/photocd.c#L430

Change that to AVCOL_TRC_IEC61966_2_4. Part 4, not 1. Then implement correct quantisation: linear RGB values are from -0.20 to 2.00, while nonlinear RGB' are from -0.43357 to 1.402278, where reference white (perfect, non-fluorescent, white-reflecting diffuser in the original scene) is 1.0, just like in BT.709. That is done by a different MATRIX THAT IS NOT just avctx->colorspace = AVCOL_SPC_BT709; and avctx->color_range = AVCOL_RANGE_JPEG.

There is also a matrix from and to sRGB in Windows XP source code that leaked. Again, I told you all that 3 years ago. Open your eyes: ​https://trac.ffmpeg.org/ticket/5923#comment:7

[Elon Musk]

Your entry is again, wrong, and full of errors.
Your understanding of this subject is pretty invalid.
Otherwise you would post patch(es) to solve this already.

[Balling]

Continue denying reality and not seeing a patch in that issue that implements own ff_yuv2rgb_coeffs.

[Balling]

​https://imgsli.com/MjE1MjQ0

You ARE denying reality, BTW. (On the left image from ​https://r0k.us/graphics/kodak/kodim23.html on the right original PCD converted to PNG with sRGB chunk ​https://www.math.purdue.edu/~lucier/PHOTO_CD/IMAGES/.)

Same is true for pcdtojpeg, FFmpeg does different colors: ​https://imgsli.com/MjE1MjQ2

[Elon Musk]

decoder outputs in yuv not rgb.

[Balling]

decoder outputs in yuv not rgb.

That is why the code changes happen in pixfmt.h and ​https://trac.ffmpeg.org/attachment/ticket/5923/ycc.diff