[FFmpeg-devel] [PATCH] avcodec/libjxlenc: add EXIF box to output (PR #21070)

[Leo Izen via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

PR #21070 opened by Leo Izen (Traneptora)
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21070
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21070.patch


>From 924a4592ade1ec883396956d89e0d0702ddfa42d Mon Sep 17 00:00:00 2001
From: Leo Izen <leo.izen@gmail.com>
Date: Mon, 1 Dec 2025 06:11:58 -0500
Subject: [PATCH 1/3] avcodec/libjxlenc: give display matrix sidedata priority

Before this commit, we ignore the display matrix side data if any EXIF
side data is present, even if that side data contains no orientation
tag. This allows us to calculate the orientation from the display
matrix sidedata first, if present. Ideally the decoder will have
removed the orientation tag upon decoding and attached the data as
display matrix side data instead, so this makes our orientation code
respect this behavior.

Signed-off-by: Leo Izen <leo.izen@gmail.com>
---
 libavcodec/libjxlenc.c | 28 +++++++++++++++++-----------
 1 file changed, 17 insertions(+), 11 deletions(-)

diff --git a/libavcodec/libjxlenc.c b/libavcodec/libjxlenc.c
index a2fec89560..8ddbfaa098 100644
--- a/libavcodec/libjxlenc.c
+++ b/libavcodec/libjxlenc.c
@@ -325,7 +325,7 @@ static int libjxl_preprocess_stream(AVCodecContext *avctx, const AVFrame *frame,
     LibJxlEncodeContext *ctx = avctx->priv_data;
     AVFrameSideData *sd;
     int32_t *matrix = (int32_t[9]){ 0 };
-    int ret = 0;
+    int ret = 0, have_matrix = 0;
     const AVPixFmtDescriptor *pix_desc = av_pix_fmt_desc_get(frame->format);
     JxlBasicInfo info;
     JxlPixelFormat *jxl_fmt = &ctx->jxl_fmt;
@@ -383,6 +383,11 @@ static int libjxl_preprocess_stream(AVCodecContext *avctx, const AVFrame *frame,
     /* bitexact lossless requires there to be no XYB transform */
     info.uses_original_profile = ctx->distance == 0.0 || !ctx->xyb;
 
+    sd = av_frame_get_side_data(frame, AV_FRAME_DATA_DISPLAYMATRIX);
+    if (sd) {
+        matrix = (int32_t *) sd->data;
+        have_matrix = 1;
+    }
     sd = av_frame_get_side_data(frame, AV_FRAME_DATA_EXIF);
     if (sd) {
         AVExifMetadata ifd = { 0 };
@@ -393,25 +398,26 @@ static int libjxl_preprocess_stream(AVCodecContext *avctx, const AVFrame *frame,
             ret = ff_exif_sanitize_ifd(avctx, frame, &ifd);
         if (ret >= 0)
             ret = av_exif_get_entry(avctx, &ifd, tag, 0, &orient);
-        if (ret >= 0 && orient && orient->value.uint[0] >= 1 && orient->value.uint[0] <= 8) {
-            av_exif_orientation_to_matrix(matrix, orient->value.uint[0]);
+        if (ret >= 0 && orient) {
+            if (!have_matrix && orient->value.uint[0] >= 1 && orient->value.uint[0] <= 8) {
+                av_exif_orientation_to_matrix(matrix, orient->value.uint[0]);
+                have_matrix = 1;
+            }
+            /* pop the orientation tag anyway, because it only creates */
+            /* ambiguity with the codestream orientation taking precdence */
             ret = av_exif_remove_entry(avctx, &ifd, tag, 0);
-        } else {
-            av_exif_orientation_to_matrix(matrix, 1);
         }
         if (ret >= 0)
             ret = av_exif_write(avctx, &ifd, &exif_buffer, AV_EXIF_TIFF_HEADER);
         if (ret < 0)
             av_log(avctx, AV_LOG_WARNING, "unable to process EXIF frame data\n");
         av_exif_free(&ifd);
-    } else {
-        sd = av_frame_get_side_data(frame, AV_FRAME_DATA_DISPLAYMATRIX);
-        if (sd)
-            matrix = (int32_t *) sd->data;
-        else
-            av_exif_orientation_to_matrix(matrix, 1);
     }
 
+    /* use identity matrix as default */
+    if (!have_matrix)
+        av_exif_orientation_to_matrix(matrix, 1);
+
     /* av_display_matrix_flip is a right-multipilcation */
     /* i.e. flip is applied before the previous matrix */
     if (frame->linesize < 0)
-- 
2.49.1


>From f1a7015a41a61d22a2ea0a006f68f6739f925e68 Mon Sep 17 00:00:00 2001
From: Leo Izen <leo.izen@gmail.com>
Date: Mon, 1 Dec 2025 06:20:58 -0500
Subject: [PATCH 2/3] avcodec/libjxlenc: avoid calling functions inside if
 statements

It leads to messier, less readable code, and can also lead to bugs.
I prefer this code style.

Signed-off-by: Leo Izen <leo.izen@gmail.com>
---
 libavcodec/libjxlenc.c | 30 +++++++++++++++++++-----------
 1 file changed, 19 insertions(+), 11 deletions(-)

diff --git a/libavcodec/libjxlenc.c b/libavcodec/libjxlenc.c
index 8ddbfaa098..67650da7e9 100644
--- a/libavcodec/libjxlenc.c
+++ b/libavcodec/libjxlenc.c
@@ -326,6 +326,7 @@ static int libjxl_preprocess_stream(AVCodecContext *avctx, const AVFrame *frame,
     AVFrameSideData *sd;
     int32_t *matrix = (int32_t[9]){ 0 };
     int ret = 0, have_matrix = 0;
+    JxlEncoderStatus jret = JXL_ENC_SUCCESS;
     const AVPixFmtDescriptor *pix_desc = av_pix_fmt_desc_get(frame->format);
     JxlBasicInfo info;
     JxlPixelFormat *jxl_fmt = &ctx->jxl_fmt;
@@ -445,7 +446,8 @@ static int libjxl_preprocess_stream(AVCodecContext *avctx, const AVFrame *frame,
         info.animation.tps_denominator = avctx->time_base.num;
     }
 
-    if (JxlEncoderSetBasicInfo(ctx->encoder, &info) != JXL_ENC_SUCCESS) {
+    jret = JxlEncoderSetBasicInfo(ctx->encoder, &info);
+    if (jret != JXL_ENC_SUCCESS) {
         av_log(avctx, AV_LOG_ERROR, "Failed to set JxlBasicInfo\n");
         ret = AVERROR_EXTERNAL;
         goto end;
@@ -457,36 +459,42 @@ static int libjxl_preprocess_stream(AVCodecContext *avctx, const AVFrame *frame,
         extra_info.bits_per_sample = info.alpha_bits;
         extra_info.exponent_bits_per_sample = info.alpha_exponent_bits;
         extra_info.alpha_premultiplied = info.alpha_premultiplied;
-
-        if (JxlEncoderSetExtraChannelInfo(ctx->encoder, 0, &extra_info) != JXL_ENC_SUCCESS) {
+        jret = JxlEncoderSetExtraChannelInfo(ctx->encoder, 0, &extra_info);
+        if (jret != JXL_ENC_SUCCESS) {
             av_log(avctx, AV_LOG_ERROR, "Failed to set JxlExtraChannelInfo for alpha!\n");
-            return AVERROR_EXTERNAL;
+            ret = AVERROR_EXTERNAL;
+            goto end;
         }
     }
 
     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");
-        sd = NULL;
+    if (sd && sd->size) {
+        jret = JxlEncoderSetICCProfile(ctx->encoder, sd->data, sd->size);
+        if (jret != JXL_ENC_SUCCESS)
+            av_log(avctx, AV_LOG_WARNING, "Could not set ICC Profile\n");
     }
 
-    if (!sd || !sd->size)
+    /* jret != JXL_ENC_SUCCESS means fallthrough from above */
+    if (!sd || !sd->size || jret != JXL_ENC_SUCCESS)
         libjxl_populate_colorspace(avctx, frame, pix_desc, &info);
 
 #if JPEGXL_NUMERIC_VERSION >= JPEGXL_COMPUTE_NUMERIC_VERSION(0, 8, 0)
-    if (JxlEncoderSetFrameBitDepth(ctx->options, &jxl_bit_depth) != JXL_ENC_SUCCESS)
+    jret = JxlEncoderSetFrameBitDepth(ctx->options, &jxl_bit_depth);
+    if (jret != JXL_ENC_SUCCESS)
         av_log(avctx, AV_LOG_WARNING, "Failed to set JxlBitDepth\n");
 #endif
 
     if (exif_buffer) {
-        if (JxlEncoderUseBoxes(ctx->encoder) != JXL_ENC_SUCCESS)
+        jret = JxlEncoderUseBoxes(ctx->encoder);
+        if (jret != JXL_ENC_SUCCESS)
             av_log(avctx, AV_LOG_WARNING, "Couldn't enable UseBoxes\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)
+        jret = JxlEncoderSetCodestreamLevel(ctx->encoder, 10);
+        if (jret != JXL_ENC_SUCCESS)
             av_log(avctx, AV_LOG_WARNING, "Could not increase codestream level\n");
     }
 
-- 
2.49.1


>From 2d6f067302dd5d60edd1a18844b8c2ab0dd6f95d Mon Sep 17 00:00:00 2001
From: Leo Izen <leo.izen@gmail.com>
Date: Mon, 1 Dec 2025 06:43:32 -0500
Subject: [PATCH 3/3] avcodec/libjxlenc: add EXIF box to output

We already parse the EXIF side data to extract the orientation, so we
should add it to the output file as an EXIF box.

Signed-off-by: Leo Izen <leo.izen@gmail.com>
---
 libavcodec/libjxlenc.c | 48 ++++++++++++++++++++++++++++++++++--------
 1 file changed, 39 insertions(+), 9 deletions(-)

diff --git a/libavcodec/libjxlenc.c b/libavcodec/libjxlenc.c
index 67650da7e9..ca46061545 100644
--- a/libavcodec/libjxlenc.c
+++ b/libavcodec/libjxlenc.c
@@ -59,6 +59,7 @@ typedef struct LibJxlEncodeContext {
     uint8_t *buffer;
     size_t buffer_size;
     JxlPixelFormat jxl_fmt;
+    AVBufferRef *exif_buffer;
 
     /* animation stuff */
     AVFrame *frame;
@@ -316,6 +317,40 @@ static int libjxl_populate_colorspace(AVCodecContext *avctx, const AVFrame *fram
     return 0;
 }
 
+static int libjxl_add_boxes(AVCodecContext *avctx)
+{
+    LibJxlEncodeContext *ctx = avctx->priv_data;
+    JxlEncoderStatus jret = JXL_ENC_SUCCESS;
+    int ret = 0, opened = 0;
+
+    /* no boxes need to be added */
+    if (!ctx->exif_buffer)
+        goto end;
+
+    jret = JxlEncoderUseBoxes(ctx->encoder);
+    if (jret != JXL_ENC_SUCCESS) {
+        av_log(avctx, AV_LOG_WARNING, "Could not enable UseBoxes\n");
+        ret = AVERROR_EXTERNAL;
+        goto end;
+    }
+    opened = 1;
+
+    jret = JxlEncoderAddBox(ctx->encoder, "Exif", ctx->exif_buffer->data, ctx->exif_buffer->size, JXL_TRUE);
+    if (jret != JXL_ENC_SUCCESS)
+        jret = JxlEncoderAddBox(ctx->encoder, "Exif", ctx->exif_buffer->data, ctx->exif_buffer->size, JXL_FALSE);
+    if (jret != JXL_ENC_SUCCESS) {
+        av_log(avctx, AV_LOG_WARNING, "Failed to add Exif box\n");
+        ret = AVERROR_EXTERNAL;
+        goto end;
+    }
+
+end:
+    if (opened)
+        JxlEncoderCloseBoxes(ctx->encoder);
+
+    return ret;
+}
+
 /**
  * Sends metadata to libjxl based on the first frame of the stream, such as pixel format,
  * orientation, bit depth, and that sort of thing.
@@ -332,7 +367,6 @@ static int libjxl_preprocess_stream(AVCodecContext *avctx, const AVFrame *frame,
     JxlPixelFormat *jxl_fmt = &ctx->jxl_fmt;
     int bits_per_sample;
     int orientation;
-    AVBufferRef *exif_buffer = NULL;
 #if JPEGXL_NUMERIC_VERSION >= JPEGXL_COMPUTE_NUMERIC_VERSION(0, 8, 0)
     JxlBitDepth jxl_bit_depth;
 #endif
@@ -409,7 +443,7 @@ static int libjxl_preprocess_stream(AVCodecContext *avctx, const AVFrame *frame,
             ret = av_exif_remove_entry(avctx, &ifd, tag, 0);
         }
         if (ret >= 0)
-            ret = av_exif_write(avctx, &ifd, &exif_buffer, AV_EXIF_TIFF_HEADER);
+            ret = av_exif_write(avctx, &ifd, &ctx->exif_buffer, AV_EXIF_T_OFF);
         if (ret < 0)
             av_log(avctx, AV_LOG_WARNING, "unable to process EXIF frame data\n");
         av_exif_free(&ifd);
@@ -484,12 +518,6 @@ static int libjxl_preprocess_stream(AVCodecContext *avctx, const AVFrame *frame,
         av_log(avctx, AV_LOG_WARNING, "Failed to set JxlBitDepth\n");
 #endif
 
-    if (exif_buffer) {
-        jret = JxlEncoderUseBoxes(ctx->encoder);
-        if (jret != JXL_ENC_SUCCESS)
-            av_log(avctx, AV_LOG_WARNING, "Couldn't enable UseBoxes\n");
-    }
-
     /* depending on basic info, level 10 might
      * be required instead of level 5 */
     if (JxlEncoderGetRequiredCodestreamLevel(ctx->encoder) > 5) {
@@ -498,8 +526,10 @@ static int libjxl_preprocess_stream(AVCodecContext *avctx, const AVFrame *frame,
             av_log(avctx, AV_LOG_WARNING, "Could not increase codestream level\n");
     }
 
+    libjxl_add_boxes(avctx);
+
 end:
-    av_buffer_unref(&exif_buffer);
+    av_buffer_unref(&ctx->exif_buffer);
     return ret;
 }
 
-- 
2.49.1

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