H264: hotfix for speedloss on frame threading and h264 files with slices.

This fix is not ideal as it still limits the multithreading on field pictures
to the 2nd field only.
Ill try to fix it properly to allow both fields to decode concurrently but this
needs more work.

This bug exists since and was caused by:
commit ea6331f8bbaf3343faec6ffe77a6218a016a3af5
Author: Ronald S. Bultje <rsbultje@gmail.com>
Date:   Mon Jun 20 10:24:33 2011 -0400

    h264-mt: fix deadlock in packets with multiple slices (e.g. MP4).

diff --git a/libavcodec/h264.c b/libavcodec/h264.c
index 4a1050dc8a6806a6d2c5767ccf98a1054547520f..07e61efb05c139a18d294a7b2d019677665f23b3 100644 (file)
--- a/libavcodec/h264.c
+++ b/libavcodec/h264.c
@@ -3710,9 +3710,13 @@ static int decode_nal_units(H264Context *h, const uint8_t *buf, int buf_size){
             switch (hx->nal_unit_type) {
                 case NAL_SPS:
                 case NAL_PPS:
+                    nals_needed = nal_index;
+                    break;
                 case NAL_IDR_SLICE:
                 case NAL_SLICE:
-                    nals_needed = nal_index;
+                    init_get_bits(&hx->s.gb, ptr, bit_length);
+                    if(!get_ue_golomb(&hx->s.gb))
+                        nals_needed = nal_index;
             }
             continue;
         }