From cbfd280f77b9e1f13beaad8cda2167646995ce3f Mon Sep 17 00:00:00 2001
From: James Almer <jamrial@gmail.com>
Date: Mon, 16 Mar 2026 18:46:21 -0300
Subject: [PATCH] avformat/lcevc: add a function to parse sequence and global
 config blocks

This exposes parsing already being done to write lvcC boxes, for the purpose
of having these values available elsewhere.
Will be useful for the following change.

Signed-off-by: James Almer <jamrial@gmail.com>
---
 libavformat/lcevc.c | 76 +++++++++++++++++++++++++++++++++++++++------
 libavformat/lcevc.h | 13 ++++++++
 2 files changed, 79 insertions(+), 10 deletions(-)

diff --git a/libavformat/lcevc.c b/libavformat/lcevc.c
index 83217c2e79..341d8d1694 100644
--- a/libavformat/lcevc.c
+++ b/libavformat/lcevc.c
@@ -30,16 +30,6 @@
 #include "avio_internal.h"
 #include "lcevc.h"
 
-typedef struct LCEVCDecoderConfigurationRecord {
-    uint8_t  profile_idc;
-    uint8_t  level_idc;
-    uint8_t  chroma_format_idc;
-    uint8_t  bit_depth_luma_minus8;
-    uint8_t  bit_depth_chroma_minus8;
-    uint32_t pic_width_in_luma_samples;
-    uint32_t pic_height_in_luma_samples;
-} LCEVCDecoderConfigurationRecord;
-
 /**
  * Rewrite the NALu stripping the unneeded blocks.
  * Given that length fields coded inside the NALu are not aware of any emulation_3bytes
@@ -187,6 +177,72 @@ static int write_nalu(LCEVCDecoderConfigurationRecord *lvcc, AVIOContext *pb,
     return 0;
 }
 
+int ff_lcvec_parse_config_record(LCEVCDecoderConfigurationRecord *lvcc,
+                                 const uint8_t *buf, int size)
+{
+    H2645Packet h2645_pkt = { 0 };
+    AVIOContext *pb;
+    int ret;
+
+    if (size <= 0)
+        return AVERROR_INVALIDDATA;
+
+    if (buf[0] == 1) {
+        GetBitContext gb;
+
+        if (size < 13)
+            return AVERROR_INVALIDDATA;
+
+        ret = init_get_bits8(&gb, buf, 13);
+        if (ret < 0)
+            return ret;
+
+        memset(lvcc, 0, sizeof(*lvcc));
+
+        skip_bits(&gb, 8);
+        lvcc->profile_idc                 = get_bits(&gb, 8);
+        lvcc->level_idc                   = get_bits(&gb, 8);
+        lvcc->chroma_format_idc           = get_bits(&gb, 2);
+        lvcc->bit_depth_luma_minus8       = get_bits(&gb, 3);
+        lvcc->bit_depth_chroma_minus8     = get_bits(&gb, 3);
+        skip_bits(&gb, 8);
+        lvcc->pic_width_in_luma_samples   = get_bits_long(&gb, 32);
+        lvcc->pic_height_in_luma_samples  = get_bits_long(&gb, 32);
+
+        return 0;
+    }
+
+    ret = ffio_open_null_buf(&pb);
+    if (ret < 0)
+        return ret;
+
+    ret = ff_h2645_packet_split(&h2645_pkt, buf, size, NULL, 0, AV_CODEC_ID_LCEVC, 0);
+    if (ret < 0)
+        goto fail;
+
+    /* look for IDR or NON_IDR */
+    for (int i = 0; i < h2645_pkt.nb_nals; i++) {
+        const H2645NAL *nal = &h2645_pkt.nals[i];
+
+        if (nal->type == LCEVC_IDR_NUT) {
+            ret = write_nalu(lvcc, pb, nal);
+            if (ret < 0)
+                goto fail;
+        } else if (nal->type == LCEVC_NON_IDR_NUT) {
+            ret = write_nalu(lvcc, pb, nal);
+            if (ret < 0)
+                goto fail;
+        }
+    }
+
+    ret = 0;
+fail:
+    ffio_close_null_buf(pb);
+    ff_h2645_packet_uninit(&h2645_pkt);
+
+    return ret;
+}
+
 int ff_isom_write_lvcc(AVIOContext *pb, const uint8_t *data, int len)
 {
     LCEVCDecoderConfigurationRecord lvcc = { 0 };
diff --git a/libavformat/lcevc.h b/libavformat/lcevc.h
index 76093c4a36..9bbc0c6764 100644
--- a/libavformat/lcevc.h
+++ b/libavformat/lcevc.h
@@ -24,6 +24,19 @@
 #include <stdint.h>
 #include "avio.h"
 
+typedef struct LCEVCDecoderConfigurationRecord {
+    uint8_t  profile_idc;
+    uint8_t  level_idc;
+    uint8_t  chroma_format_idc;
+    uint8_t  bit_depth_luma_minus8;
+    uint8_t  bit_depth_chroma_minus8;
+    uint32_t pic_width_in_luma_samples;
+    uint32_t pic_height_in_luma_samples;
+} LCEVCDecoderConfigurationRecord;
+
 int ff_isom_write_lvcc(AVIOContext *pb, const uint8_t *data, int len);
 
+int ff_lcvec_parse_config_record(LCEVCDecoderConfigurationRecord *lvcc,
+                                 const uint8_t *buf, int size);
+
 #endif /* AVFORMAT_LCEVC_H */