[FFmpeg-devel] [PATCH 5/5] avcodec/bsf/vvc_mp4toannexb: Don't realloc when creating new extradata

[Andreas Rheinhardt]

AVCodecParameters.extradata is supposed to be allocated with
av_malloc(); av_realloc() and its wrappers do not guarantee
the proper alignment. Therefore parse the extradata twice:
Once to check its validity and to determine the eventual size
and a second time to actually write the new extradata.

(Of course, not reallocating the buffer is beneficial in itself.)

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at outlook.com>
---
 libavcodec/bsf/vvc_mp4toannexb.c | 51 ++++++++++++++++----------------
 1 file changed, 25 insertions(+), 26 deletions(-)

diff --git a/libavcodec/bsf/vvc_mp4toannexb.c b/libavcodec/bsf/vvc_mp4toannexb.c
index bfb0338116..1879c1fab9 100644
--- a/libavcodec/bsf/vvc_mp4toannexb.c
+++ b/libavcodec/bsf/vvc_mp4toannexb.c
@@ -38,13 +38,11 @@ typedef struct VVCBSFContext {
 } VVCBSFContext;
 
 static int vvc_extradata_to_annexb_internal(void *logctx, GetByteContext *gb,
-                                            uint8_t **new_extradatap,
+                                            uint8_t *new_extradata,
                                             size_t *new_extradata_sizep)
 {
     int num_arrays = bytestream2_get_byte(gb);
-    uint8_t *new_extradata = NULL;
     size_t new_extradata_size = 0;
-    int ret;
 
     for (int i = 0; i < num_arrays; i++) {
         int cnt;
@@ -55,15 +53,15 @@ static int vvc_extradata_to_annexb_internal(void *logctx, GetByteContext *gb,
         else
             cnt = bytestream2_get_be16(gb);
 
-        av_log(logctx, AV_LOG_DEBUG, "nalu_type %d cnt %d\n", type, cnt);
+        if (!new_extradata)
+            av_log(logctx, AV_LOG_DEBUG, "nalu_type %d cnt %d\n", type, cnt);
 
         if (!(type == VVC_OPI_NUT || type == VVC_DCI_NUT ||
               type == VVC_VPS_NUT || type == VVC_SPS_NUT || type == VVC_PPS_NUT
               || type == VVC_PREFIX_SEI_NUT || type == VVC_SUFFIX_SEI_NUT)) {
             av_log(logctx, AV_LOG_ERROR,
                    "Invalid NAL unit type in extradata: %d\n", type);
-            ret = AVERROR_INVALIDDATA;
-            goto fail;
+            return AVERROR_INVALIDDATA;
         }
 
         for (int j = 0; j < cnt; j++) {
@@ -72,30 +70,21 @@ static int vvc_extradata_to_annexb_internal(void *logctx, GetByteContext *gb,
             if (!nalu_len ||
                 nalu_len > bytestream2_get_bytes_left(gb) ||
                 4 + nalu_len > FFMIN(INT_MAX, SIZE_MAX) - AV_INPUT_BUFFER_PADDING_SIZE - new_extradata_size) {
-                ret = AVERROR_INVALIDDATA;
-                goto fail;
+                return AVERROR_INVALIDDATA;
             }
-            ret = av_reallocp(&new_extradata, new_extradata_size + nalu_len + 4
-                              + AV_INPUT_BUFFER_PADDING_SIZE);
-            if (ret < 0)
-                goto fail;
-
-            AV_WB32(new_extradata + new_extradata_size, 1); // add the startcode
-            bytestream2_get_buffer(gb, new_extradata + new_extradata_size + 4,
-                                   nalu_len);
+            if (new_extradata) {
+                AV_WB32(new_extradata + new_extradata_size, 1); // add the startcode
+                bytestream2_get_bufferu(gb, new_extradata + new_extradata_size + 4,
+                                        nalu_len);
+            } else
+                bytestream2_skipu(gb, nalu_len);
             new_extradata_size += 4 + nalu_len;
-            memset(new_extradata + new_extradata_size, 0,
-                   AV_INPUT_BUFFER_PADDING_SIZE);
         }
     }
 
-    *new_extradatap      = new_extradata;
     *new_extradata_sizep = new_extradata_size;
 
     return 0;
-fail:
-    av_freep(&new_extradata);
-    return ret;
 }
 
 static int vvc_extradata_to_annexb(AVBSFContext *ctx)
@@ -193,10 +182,20 @@ static int vvc_extradata_to_annexb(AVBSFContext *ctx)
                max_picture_width, max_picture_height, avg_frame_rate);
     }
 
-    ret = vvc_extradata_to_annexb_internal(ctx, &gb, &new_extradata,
-                                           &new_extradata_size);
-    if (ret < 0)
-        return ret;
+    while (1) {
+        GetByteContext gb_bak = gb;
+        ret = vvc_extradata_to_annexb_internal(ctx, &gb, new_extradata,
+                                               &new_extradata_size);
+        if (ret < 0)
+            return ret;
+        if (new_extradata || !new_extradata_size)
+            break;
+        new_extradata = av_malloc(new_extradata_size + AV_INPUT_BUFFER_PADDING_SIZE);
+        if (!new_extradata)
+            return AVERROR(ENOMEM);
+        memset(new_extradata + new_extradata_size, 0, AV_INPUT_BUFFER_PADDING_SIZE);
+        gb = gb_bak;
+    }
 
     av_freep(&ctx->par_out->extradata);
     ctx->par_out->extradata = new_extradata;
-- 
2.34.1