avcodec/h264: Do not fail with randomly truncated VUIs

Fixes Ticket4445
Tested-by: Vittorio Giovara <vittorio.giovara@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/h264.c

@@ -1634,7 +1634,9 @@ again:
                 break;
             case NAL_SPS:
                 init_get_bits(&h->gb, ptr, bit_length);
-                if (ff_h264_decode_seq_parameter_set(h) < 0 && (h->is_avc ? nalsize : 1)) {
+                if (ff_h264_decode_seq_parameter_set(h, 0) >= 0)
+                    break;
+                if (h->is_avc ? nalsize : 1) {
                     av_log(h->avctx, AV_LOG_DEBUG,
                            "SPS decoding failure, trying again with the complete NAL\n");
                     if (h->is_avc)
@@ -1643,8 +1645,11 @@ again:
                         break;
                     init_get_bits(&h->gb, &buf[buf_index + 1 - consumed],
                                   8*(next_avc - buf_index + consumed - 1));
-                    ff_h264_decode_seq_parameter_set(h);
+                    if (ff_h264_decode_seq_parameter_set(h, 0) >= 0)
+                        break;
                 }
+                init_get_bits(&h->gb, ptr, bit_length);
+                ff_h264_decode_seq_parameter_set(h, 1);
 
                 break;
             case NAL_PPS:

libavcodec/h264.h

@@ -812,7 +812,7 @@ int ff_h264_decode_sei(H264Context *h);
 /**
  * Decode SPS
  */
-int ff_h264_decode_seq_parameter_set(H264Context *h);
+int ff_h264_decode_seq_parameter_set(H264Context *h, int ignore_truncation);
 
 /**
  * compute profile from sps

libavcodec/h264_parser.c

@@ -282,7 +282,7 @@ static inline int parse_nal_units(AVCodecParserContext *s,
         init_get_bits(&h->gb, ptr, 8 * dst_length);
         switch (h->nal_unit_type) {
         case NAL_SPS:
-            ff_h264_decode_seq_parameter_set(h);
+            ff_h264_decode_seq_parameter_set(h, 0);
             break;
         case NAL_PPS:
             ff_h264_decode_picture_parameter_set(h, h->gb.size_in_bits);

libavcodec/h264_ps.c

@@ -297,7 +297,7 @@ static void decode_scaling_matrices(H264Context *h, SPS *sps,
     }
 }
 
-int ff_h264_decode_seq_parameter_set(H264Context *h)
+int ff_h264_decode_seq_parameter_set(H264Context *h, int ignore_truncation)
 {
     int profile_idc, level_idc, constraint_set_flags = 0;
     unsigned int sps_id;
@@ -518,8 +518,9 @@ int ff_h264_decode_seq_parameter_set(H264Context *h)
     }
 
     if (get_bits_left(&h->gb) < 0) {
-        av_log(h->avctx, AV_LOG_ERROR,
+        av_log(h->avctx, ignore_truncation ? AV_LOG_WARNING : AV_LOG_ERROR,
                "Overread %s by %d bits\n", sps->vui_parameters_present_flag ? "VUI" : "SPS", -get_bits_left(&h->gb));
+        if (!ignore_truncation)
             goto fail;
     }