[FFmpeg-devel] [PATCH 3/5] avcodec/bsf/hevc_mp4toannexb: Don't realloc when creating new extradata

[Andreas Rheinhardt <andreas.rheinhardt@outlook.com>]

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@outlook.com>
---
 libavcodec/bsf/hevc_mp4toannexb.c | 44 +++++++++++++++----------------
 1 file changed, 22 insertions(+), 22 deletions(-)

diff --git a/libavcodec/bsf/hevc_mp4toannexb.c b/libavcodec/bsf/hevc_mp4toannexb.c
index a695cba370..f5424e95b8 100644
--- a/libavcodec/bsf/hevc_mp4toannexb.c
+++ b/libavcodec/bsf/hevc_mp4toannexb.c
@@ -38,13 +38,11 @@ typedef struct HEVCBSFContext {
 } HEVCBSFContext;
 
 static int hevc_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 type = bytestream2_get_byte(gb) & 0x3f;
@@ -54,8 +52,7 @@ static int hevc_extradata_to_annexb_internal(void *logctx, GetByteContext *gb,
               type == HEVC_NAL_SEI_PREFIX || type == HEVC_NAL_SEI_SUFFIX)) {
             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++) {
@@ -64,26 +61,19 @@ static int hevc_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 hevc_extradata_to_annexb(AVBSFContext *ctx)
@@ -100,10 +90,20 @@ static int hevc_extradata_to_annexb(AVBSFContext *ctx)
     bytestream2_skip(&gb, 21);
     length_size = (bytestream2_get_byte(&gb) & 3) + 1;
 
-    ret = hevc_extradata_to_annexb_internal(ctx, &gb, &new_extradata,
-                                            &new_extradata_size);
-    if (ret < 0)
-        return ret;
+    while (1) {
+        GetByteContext gb_bak = gb;
+        ret = hevc_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

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