[FFmpeg-devel] [PATCH v9 2/2] avcodec/libjxlenc: properly read input colorspace

[Leo Izen <leo.izen@gmail.com>]

Whether an ICC profile is present or not, the libjxl
encoder wrapper should now properly read colorspace tags
and forward them to libjxl appropriately, rather than just
assume sRGB as before. It will also print warnings when
colorimetric assumptions are made about the input data.
---
 libavcodec/libjxlenc.c | 153 +++++++++++++++++++++++++++++++++--------
 1 file changed, 123 insertions(+), 30 deletions(-)

diff --git a/libavcodec/libjxlenc.c b/libavcodec/libjxlenc.c
index 8bebec6aeb..6a948cc3ae 100644
--- a/libavcodec/libjxlenc.c
+++ b/libavcodec/libjxlenc.c
@@ -27,6 +27,7 @@
 #include <string.h>
 
 #include "libavutil/avutil.h"
+#include "libavutil/csp.h"
 #include "libavutil/error.h"
 #include "libavutil/frame.h"
 #include "libavutil/libm.h"
@@ -117,7 +118,7 @@ static int libjxl_init_jxl_encoder(AVCodecContext *avctx)
         return AVERROR_EXTERNAL;
     }
 
-    /* check for negative zero, our default */
+    /* check for negative, our default */
     if (ctx->distance < 0.0) {
         /* use ffmpeg.c -q option if passed */
         if (avctx->flags & AV_CODEC_FLAG_QSCALE)
@@ -133,7 +134,7 @@ static int libjxl_init_jxl_encoder(AVCodecContext *avctx)
      */
     if (ctx->distance > 0.0 && ctx->distance < 0.01)
         ctx->distance = 0.01;
-    if (JxlEncoderOptionsSetDistance(ctx->options, ctx->distance) != JXL_ENC_SUCCESS) {
+    if (JxlEncoderSetFrameDistance(ctx->options, ctx->distance) != JXL_ENC_SUCCESS) {
         av_log(avctx, AV_LOG_ERROR, "Failed to set distance: %f\n", ctx->distance);
         return AVERROR_EXTERNAL;
     }
@@ -185,6 +186,52 @@ static av_cold int libjxl_encode_init(AVCodecContext *avctx)
     return 0;
 }
 
+/**
+ * Populate a JxlColorEncoding with the given enum AVColorPrimaries.
+ * @return < 0 upon failure, >= 0 upon success
+ */
+static int libjxl_populate_primaries(JxlColorEncoding *jxl_color, enum AVColorPrimaries prm)
+{
+    const AVColorPrimariesDesc *desc;
+
+    switch (prm) {
+    case AVCOL_PRI_BT709:
+        jxl_color->primaries = JXL_PRIMARIES_SRGB;
+        jxl_color->white_point = JXL_WHITE_POINT_D65;
+        return 0;
+    case AVCOL_PRI_BT2020:
+        jxl_color->primaries = JXL_PRIMARIES_2100;
+        jxl_color->white_point = JXL_WHITE_POINT_D65;
+        return 0;
+    case AVCOL_PRI_SMPTE431:
+        jxl_color->primaries = JXL_PRIMARIES_P3;
+        jxl_color->white_point = JXL_WHITE_POINT_DCI;
+        return 0;
+    case AVCOL_PRI_SMPTE432:
+        jxl_color->primaries = JXL_PRIMARIES_P3;
+        jxl_color->white_point = JXL_WHITE_POINT_D65;
+        return 0;
+    }
+
+    desc = av_csp_primaries_desc_from_id(prm);
+    if (!desc)
+        return AVERROR(EINVAL);
+
+    jxl_color->primaries = JXL_PRIMARIES_CUSTOM;
+    jxl_color->white_point = JXL_WHITE_POINT_CUSTOM;
+
+    jxl_color->primaries_red_xy[0] = av_q2d(desc->prim.r.x);
+    jxl_color->primaries_red_xy[1] = av_q2d(desc->prim.r.y);
+    jxl_color->primaries_green_xy[0] = av_q2d(desc->prim.g.x);
+    jxl_color->primaries_green_xy[1] = av_q2d(desc->prim.g.y);
+    jxl_color->primaries_blue_xy[0] = av_q2d(desc->prim.b.x);
+    jxl_color->primaries_blue_xy[1] = av_q2d(desc->prim.b.y);
+    jxl_color->white_point_xy[0] = av_q2d(desc->wp.x);
+    jxl_color->white_point_xy[1] = av_q2d(desc->wp.y);
+
+    return 0;
+}
+
 /**
  * Encode an entire frame. Currently animation, is not supported by
  * this encoder, so this will always reinitialize a new still image
@@ -223,49 +270,95 @@ static int libjxl_encode_frame(AVCodecContext *avctx, AVPacket *pkt, const AVFra
         info.exponent_bits_per_sample = info.bits_per_sample > 16 ? 8 : 5;
         info.alpha_exponent_bits = info.alpha_bits ? info.exponent_bits_per_sample : 0;
         jxl_fmt.data_type = info.bits_per_sample > 16 ? JXL_TYPE_FLOAT : JXL_TYPE_FLOAT16;
-        JxlColorEncodingSetToLinearSRGB(&jxl_color, info.num_color_channels == 1);
     } else {
         info.exponent_bits_per_sample = 0;
         info.alpha_exponent_bits = 0;
         jxl_fmt.data_type = info.bits_per_sample <= 8 ? JXL_TYPE_UINT8 : JXL_TYPE_UINT16;
-        JxlColorEncodingSetToSRGB(&jxl_color, info.num_color_channels == 1);
     }
 
-    if (info.bits_per_sample > 16
-        || info.xsize > (1 << 18) || info.ysize > (1 << 18)
-        || (info.xsize << 4) * (info.ysize << 4) > (1 << 20)) {
-        /*
-         * must upgrade codestream to level 10, from level 5
-         * the encoder will not do this automatically
-         */
-        if (JxlEncoderSetCodestreamLevel(ctx->encoder, 10) != JXL_ENC_SUCCESS) {
-            av_log(avctx, AV_LOG_ERROR, "Could not upgrade JXL Codestream level.\n");
-            return AVERROR_EXTERNAL;
-        }
-    }
+    /* JPEG XL format itself does not support limited range */
+    if (avctx->color_range == AVCOL_RANGE_MPEG ||
+        avctx->color_range == AVCOL_RANGE_UNSPECIFIED && frame->color_range == AVCOL_RANGE_MPEG)
+        av_log(avctx, AV_LOG_WARNING, "This encoder does not support limited (tv) range, colors will be wrong!\n");
+    else if (avctx->color_range != AVCOL_RANGE_JPEG && frame->color_range != AVCOL_RANGE_JPEG)
+        av_log(avctx, AV_LOG_WARNING, "Unknown color range, assuming full (pc)\n");
 
     /* bitexact lossless requires there to be no XYB transform */
     info.uses_original_profile = ctx->distance == 0.0;
 
-    sd = av_frame_get_side_data(frame, AV_FRAME_DATA_ICC_PROFILE);
-    if (sd && sd->size && JxlEncoderSetICCProfile(ctx->encoder, sd->data, sd->size) != JXL_ENC_SUCCESS) {
-        av_log(avctx, AV_LOG_WARNING, "Could not set ICC Profile\n");
-    } else if (info.uses_original_profile) {
-        /*
-        * the color encoding is not used if uses_original_profile is false
-        * this just works around a bug in libjxl 0.7.0 and lower
-        */
-        if (JxlEncoderSetColorEncoding(ctx->encoder, &jxl_color) != JXL_ENC_SUCCESS) {
-            av_log(avctx, AV_LOG_ERROR, "Failed to set JxlColorEncoding\n");
-            return AVERROR_EXTERNAL;
-        }
-    }
-
     if (JxlEncoderSetBasicInfo(ctx->encoder, &info) != JXL_ENC_SUCCESS) {
         av_log(avctx, AV_LOG_ERROR, "Failed to set JxlBasicInfo\n");
         return AVERROR_EXTERNAL;
     }
 
+    /* rendering intent doesn't matter here
+     * but libjxl will whine if we don't set it */
+    jxl_color.rendering_intent = JXL_RENDERING_INTENT_RELATIVE;
+
+    switch (frame->color_trc && frame->color_trc != AVCOL_TRC_UNSPECIFIED
+            ? frame->color_trc : avctx->color_trc) {
+    case AVCOL_TRC_BT709:
+        jxl_color.transfer_function = JXL_TRANSFER_FUNCTION_709;
+        break;
+    case AVCOL_TRC_LINEAR:
+        jxl_color.transfer_function = JXL_TRANSFER_FUNCTION_LINEAR;
+        break;
+    case AVCOL_TRC_IEC61966_2_1:
+        jxl_color.transfer_function = JXL_TRANSFER_FUNCTION_SRGB;
+        break;
+    case AVCOL_TRC_SMPTE428:
+        jxl_color.transfer_function = JXL_TRANSFER_FUNCTION_DCI;
+        break;
+    case AVCOL_TRC_SMPTE2084:
+        jxl_color.transfer_function = JXL_TRANSFER_FUNCTION_PQ;
+        break;
+    case AVCOL_TRC_ARIB_STD_B67:
+        jxl_color.transfer_function = JXL_TRANSFER_FUNCTION_HLG;
+        break;
+    case AVCOL_TRC_GAMMA22:
+        jxl_color.transfer_function = JXL_TRANSFER_FUNCTION_GAMMA;
+        jxl_color.gamma = 2.2;
+        break;
+    case AVCOL_TRC_GAMMA28:
+        jxl_color.transfer_function = JXL_TRANSFER_FUNCTION_GAMMA;
+        jxl_color.gamma = 2.8;
+        break;
+    default:
+        if (pix_desc->flags & AV_PIX_FMT_FLAG_FLOAT) {
+            av_log(avctx, AV_LOG_WARNING, "Unknown transfer function, assuming Linear Light. Colors may be wrong.\n");
+            jxl_color.transfer_function = JXL_TRANSFER_FUNCTION_LINEAR;
+        } else {
+            av_log(avctx, AV_LOG_WARNING, "Unknown transfer function, assuming IEC61966-2-1/sRGB. Colors may be wrong.\n");
+            jxl_color.transfer_function = JXL_TRANSFER_FUNCTION_SRGB;
+        }
+    }
+
+    /* This should be implied to be honest
+     * but a libjxl bug makes it fail otherwise */
+    if (info.num_color_channels == 1)
+        jxl_color.color_space = JXL_COLOR_SPACE_GRAY;
+    else
+        jxl_color.color_space = JXL_COLOR_SPACE_RGB;
+
+    ret = libjxl_populate_primaries(&jxl_color,
+            frame->color_primaries && frame->color_primaries != AVCOL_PRI_UNSPECIFIED
+            ? frame->color_primaries : avctx->color_primaries);
+    if (ret < 0)
+        return ret;
+
+    sd = av_frame_get_side_data(frame, AV_FRAME_DATA_ICC_PROFILE);
+    if (sd && sd->size && JxlEncoderSetICCProfile(ctx->encoder, sd->data, sd->size) != JXL_ENC_SUCCESS)
+        av_log(avctx, AV_LOG_WARNING, "Could not set ICC Profile\n");
+    if (JxlEncoderSetColorEncoding(ctx->encoder, &jxl_color) != JXL_ENC_SUCCESS)
+        av_log(avctx, AV_LOG_WARNING, "Failed to set JxlColorEncoding\n");
+
+    /* depending on basic info, level 10 might
+     * be required instead of level 5 */
+    if (JxlEncoderGetRequiredCodestreamLevel(ctx->encoder) > 5) {
+        if (JxlEncoderSetCodestreamLevel(ctx->encoder, 10) != JXL_ENC_SUCCESS)
+            av_log(avctx, AV_LOG_WARNING, "Could not increase codestream level\n");
+    }
+
     jxl_fmt.endianness = JXL_NATIVE_ENDIAN;
     jxl_fmt.align = frame->linesize[0];
 
-- 
2.36.1

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