Wan-Teh Chang
Wan-Teh Chang
Hi Dirk, The `CSP_VERTICAL` and `CSP_COLOCATED` chroma sample positions for 4:2:0 in the AV1 spec are commonly used for videos. The chroma sample position commonly used for 4:2:0 still images...
Note that the YCbCr-to-RGB conversion functions in libheif/heif_colorconversion.cc also assume the center chroma sample position. For example, in `Op_YCbCr420_to_RGB24::convert_colorspace(()`, we have: ``` int x, y; for (y = 0; y...
Hi Dirk, Thank you for looking up the 4:2:2 chroma sample position in JPEG. Leo Barnes told me the same thing. How we should handle 4:2:2 in AVIF is a...
@farindk @fancycode Please review. Thanks. There is more than one way to fix the mismatches. Please let me know if you prefer a different fix.
I abandoned this pull request. I believe the issue has been fixed.
@svgeesus Chris: The libavif issue https://github.com/AOMediaCodec/libavif/issues/1421 that you mentioned in https://github.com/w3c/PNG-spec/issues/312#issuecomment-1979051651 covers conversion of AVIF to both PNG and JPEG. The PNG part of that libavif issue is already [fixed](https://github.com/AOMediaCodec/libavif/pull/1422)....
The early return from `png_handle_PLTE()` that I referred to is the folllowing: ``` 952 #ifndef PNG_READ_OPT_PLTE_SUPPORTED 953 if (png_ptr->color_type != PNG_COLOR_TYPE_PALETTE) 954 { 955 png_crc_finish(png_ptr, length); 956 return; 957 }...
John: Thank you for taking a look. I am not familiar with libpng. (I remember I spotted this dead code while debugging https://github.com/glennrp/libpng/issues/482.) I am afraid that I don't know...
John: I just wrote a test Chrome changelist (patch) of your suggested change: https://chromium-review.googlesource.com/c/chromium/src/+/5005531 I sent the changelist to Chrome's commit queue dry run. I will report back if it...
@kleisauke Hi Kleis. I analyzed the code. There is an important difference between calling `aom_codec_control(&codec, AV1E_SET_ENABLE_INTRABC, 0)` and setting `sf->mv_sf.use_intrabc` to 0: the `aom_codec_control(&codec, AV1E_SET_ENABLE_INTRABC, 0)` call will cause `cpi->common.features.allow_intrabc`...