[FFmpeg-devel] [PATCH] h2645_parse: support badly muxed mp4 streams

[Hendrik Leppkes]

Some streams contain an additional AnnexB NAL inside the mp4/nalff NALU.
This commonly occurs in interlaced streams where both fields are packed
into the same MP4 NAL with an AnnexB startcode in between.

Port handling of this format from the previous h264 nal handling.

Fixes trac #5529
---
 libavcodec/h2645_parse.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/libavcodec/h2645_parse.c b/libavcodec/h2645_parse.c
index 62d0447..c0dda79 100644
--- a/libavcodec/h2645_parse.c
+++ b/libavcodec/h2645_parse.c
@@ -250,6 +250,7 @@ int ff_h2645_packet_split(H2645Packet *pkt, const uint8_t *buf, int length,
                           enum AVCodecID codec_id)
 {
     int consumed, ret = 0;
+    const uint8_t *next_avc = is_nalff ? buf : buf + length;
 
     pkt->nb_nals = 0;
     while (length >= 4) {
@@ -257,7 +258,7 @@ int ff_h2645_packet_split(H2645Packet *pkt, const uint8_t *buf, int length,
         int extract_length = 0;
         int skip_trailing_zeros = 1;
 
-        if (is_nalff) {
+        if (buf >= next_avc) {
             int i;
             for (i = 0; i < nal_length_size; i++)
                 extract_length = (extract_length << 8) | buf[i];
@@ -268,6 +269,7 @@ int ff_h2645_packet_split(H2645Packet *pkt, const uint8_t *buf, int length,
                 av_log(logctx, AV_LOG_ERROR, "Invalid NAL unit size.\n");
                 return AVERROR_INVALIDDATA;
             }
+            next_avc = buf + extract_length;
         } else {
             /* search start code */
             while (buf[0] != 0 || buf[1] != 0 || buf[2] != 1) {
@@ -282,12 +284,22 @@ int ff_h2645_packet_split(H2645Packet *pkt, const uint8_t *buf, int length,
                         av_log(logctx, AV_LOG_ERROR, "No start code is found.\n");
                         return AVERROR_INVALIDDATA;
                     }
+                } else if (buf >= (next_avc - 3)) {
+                    /* skip straight to the end, right before the next NAL
+                       (offset by 3 for the code below) */
+                    int remaining = next_avc - buf - 3;
+                    buf    += remaining;
+                    length -= remaining;
+                    break;
                 }
             }
 
             buf           += 3;
             length        -= 3;
             extract_length = length;
+
+            if (buf >= next_avc)
+                continue;
         }
 
         if (pkt->nals_allocated < pkt->nb_nals + 1) {
@@ -315,6 +327,11 @@ int ff_h2645_packet_split(H2645Packet *pkt, const uint8_t *buf, int length,
         if (consumed < 0)
             return consumed;
 
+        if (is_nalff && (extract_length != consumed) && extract_length)
+            av_log(logctx, AV_LOG_DEBUG,
+                   "NALFF: Consumed only %d bytes instead of %d\n",
+                   consumed, extract_length);
+
         pkt->nb_nals++;
 
         /* see commit 3566042a0 */
-- 
2.7.2.windows.1