[PR] avutil/hdr_dynamic_metadata: fix from_t35 NULL return and version doc (PR #24013)

PR #24013 opened by Marcos Ashton (MarcosAsh)
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/24013
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/24013.patch

## Summary
av_dynamic_hdr_plus_from_t35() returns AVERROR(ENOMEM) when passed a NULL AVDynamicHDRPlus. A NULL output struct is invalid API usage by the caller, not an allocation failure, and nothing is allocated on that path. av_dynamic_hdr_smpte2094_app5_from_t35() already returns AVERROR(EINVAL) for the same condition.

This switches it to AVERROR(EINVAL) so the two parsers agree. Both in-tree callers (libavformat/matroskadec.c and libavcodec/itut35.c) allocate the struct before calling and only propagate the return value, so neither changes behavior.

Also corrects the documentation for AVDynamicHDRPlus.application_version, which says the value shall be set to 0. That contradicts both sides of the implementation: av_dynamic_hdr_plus_to_t35() ignores the field and always writes 1, the value CTA-861-H specifies for the HDR10+ payload, and av_dynamic_hdr_plus_from_t35() sets it from the parsed payload rather than validating it against 0. No in-tree code assigns the field.


>From 01b5a15c68b80a10bb3dac5691aef1adad953bde Mon Sep 17 00:00:00 2001
From: Marcos Ashton Iglesias <[email protected]>
Date: Tue, 4 Aug 2026 22:15:17 +0100
Subject: [PATCH] avutil/hdr_dynamic_metadata: fix from_t35 NULL return and
 version doc

av_dynamic_hdr_plus_from_t35() returned AVERROR(ENOMEM) when passed a
NULL AVDynamicHDRPlus. A NULL output struct is invalid API usage by the
caller, not an allocation failure, and nothing is allocated on that
path. av_dynamic_hdr_smpte2094_app5_from_t35() already returns
AVERROR(EINVAL) for the same condition; make the two parsers agree.

The documentation for AVDynamicHDRPlus.application_version said the
value shall be set to 0, which contradicts both sides of the
implementation: av_dynamic_hdr_plus_to_t35() ignores the field and
always writes 1, the value CTA-861-H specifies for the HDR10+ payload,
and av_dynamic_hdr_plus_from_t35() sets the field from the parsed
payload rather than validating it against 0. No FFmpeg code assigns
this field, so document the contract the implementation provides.

Signed-off-by: marcos ashton <[email protected]>
---
 libavutil/hdr_dynamic_metadata.c | 2 +-
 libavutil/hdr_dynamic_metadata.h | 6 +++++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/libavutil/hdr_dynamic_metadata.c b/libavutil/hdr_dynamic_metadata.c
index 9c89625421..4c9ac25970 100644
--- a/libavutil/hdr_dynamic_metadata.c
+++ b/libavutil/hdr_dynamic_metadata.c
@@ -64,7 +64,7 @@ int av_dynamic_hdr_plus_from_t35(AVDynamicHDRPlus *s, const uint8_t *data,
     int ret;
 
     if (!s)
-        return AVERROR(ENOMEM);
+        return AVERROR(EINVAL);
 
     if (size > AV_HDR_PLUS_MAX_PAYLOAD_SIZE)
         return AVERROR(EINVAL);
diff --git a/libavutil/hdr_dynamic_metadata.h b/libavutil/hdr_dynamic_metadata.h
index a051ac7471..5881c35220 100644
--- a/libavutil/hdr_dynamic_metadata.h
+++ b/libavutil/hdr_dynamic_metadata.h
@@ -248,7 +248,11 @@ typedef struct AVDynamicHDRPlus {
 
     /**
      * Application version in the application defining document in ST-2094
-     * suite. The value shall be set to 0.
+     * suite. CTA-861-H sets this to 1 for the HDR10+ payload carried in a
+     * Rec. ITU-T T.35 message.
+     *
+     * av_dynamic_hdr_plus_from_t35() sets this field from the parsed payload.
+     * av_dynamic_hdr_plus_to_t35() ignores it and always writes 1.
      */
     uint8_t application_version;
 
-- 
2.52.0

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