h264_mp3toannexb_bsg: don't crash, but warn, if PPS/SPS not found.

Should an AVC-1 in MP4 stream not contain SPS or PPS NAL units,
this BSF is then unable to allocate an output buffer for the
modified stream. Warn that the resulting stream may be unplayable.

Fix roundup issue #2386.

Signed-off-by: Ronald S. Bultje <rsbultje@gmail.com>
(cherry picked from commit 02dd3666c2)

libavcodec/h264_mp4toannexb_bsf.c

@@ -75,7 +75,7 @@ static int h264_mp4toannexb_filter(AVBitStreamFilterContext *bsfc,
     if (!ctx->extradata_parsed) {
         uint16_t unit_size;
         uint64_t total_size = 0;
-        uint8_t *out = NULL, unit_nb, sps_done = 0;
+        uint8_t *out = NULL, unit_nb, sps_done = 0, sps_seen = 0, pps_seen = 0;
         const uint8_t *extradata = avctx->extradata+4;
         static const uint8_t nalu_header[4] = {0, 0, 0, 1};
 
@@ -89,7 +89,15 @@ static int h264_mp4toannexb_filter(AVBitStreamFilterContext *bsfc,
         if (!unit_nb) {
             unit_nb = *extradata++; /* number of pps unit(s) */
             sps_done++;
+
+            if (unit_nb)
+                pps_seen = 1;
+        }
+        else
+        {
+            sps_seen = 1;
         }
+
         while (unit_nb--) {
             void *tmp;
 
@@ -114,7 +122,14 @@ static int h264_mp4toannexb_filter(AVBitStreamFilterContext *bsfc,
                 unit_nb = *extradata++; /* number of pps unit(s) */
         }
 
-        memset(out + total_size, 0, FF_INPUT_BUFFER_PADDING_SIZE);
+        if(out)
+            memset(out + total_size, 0, FF_INPUT_BUFFER_PADDING_SIZE);
+
+        if (!sps_seen)
+            av_log(avctx, AV_LOG_WARNING, "Warning: SPS NALU missing or invalid. The resulting stream may not play.\n");
+        if (!pps_seen)
+            av_log(avctx, AV_LOG_WARNING, "Warning: PPS NALU missing or invalid. The resulting stream may not play.\n");
+
         av_free(avctx->extradata);
         avctx->extradata      = out;
         avctx->extradata_size = total_size;