[FFmpeg-devel] [PATCH v2 09/18] avcodec/libjxlenc: also attach extra channel info

[Niklas Haas <ffmpeg@haasn.xyz>]

From: Niklas Haas <git@haasn.dev>

Works around a bug where older versions of libjxl don't correctly forward
the alpha channel information to the extra channel info.
---
 libavcodec/libjxlenc.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/libavcodec/libjxlenc.c b/libavcodec/libjxlenc.c
index 924a835436..5a062b8d0d 100644
--- a/libavcodec/libjxlenc.c
+++ b/libavcodec/libjxlenc.c
@@ -394,6 +394,19 @@ static int libjxl_preprocess_stream(AVCodecContext *avctx, const AVFrame *frame,
         return AVERROR_EXTERNAL;
     }
 
+    if (info.alpha_bits) {
+        JxlExtraChannelInfo extra_info;
+        JxlEncoderInitExtraChannelInfo(JXL_CHANNEL_ALPHA, &extra_info);
+        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) {
+            av_log(avctx, AV_LOG_ERROR, "Failed to set JxlExtraChannelInfo for channel %d\n", i);
+            return AVERROR_EXTERNAL;
+        }
+    }
+
     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");
-- 
2.50.1

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