[FFmpeg-devel] [PATCH 5/6] h264_redundant_pps: Make it reference-compatible

Andreas Rheinhardt andreas.rheinhardt at googlemail.com
Fri Nov 9 07:31:37 EET 2018


Since c6a63e11092c975b89d824f08682fe31948d3686, the parameter sets
modified as content of PPS units were references shared with the
CodedBitsreamH264Context, so modifying them alters the parsing process
of future access units which meant that frames often got discarded
because invalid values were parsed. This patch makes h264_redundant_pps
compatible with the reality of reference-counted parameter sets.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at googlemail.com>
---
 libavcodec/h264_redundant_pps_bsf.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/libavcodec/h264_redundant_pps_bsf.c b/libavcodec/h264_redundant_pps_bsf.c
index 79a11c0e30..059eb4d2a7 100644
--- a/libavcodec/h264_redundant_pps_bsf.c
+++ b/libavcodec/h264_redundant_pps_bsf.c
@@ -40,8 +40,17 @@ typedef struct H264RedundantPPSContext {
 
 
 static int h264_redundant_pps_fixup_pps(H264RedundantPPSContext *ctx,
-                                        H264RawPPS *pps)
+                                        CodedBitstreamUnit *unit)
 {
+    H264RawPPS *pps;
+    int err;
+    // The changes we are about to perform affect the parsing process,
+    // so we must make sure that the PPS is writeable, otherwise the
+    // parsing of the headers will be incorrect and even raise errors.
+    if ((err = ff_cbs_h264_make_pps_writeable(&unit->content_ref)) < 0)
+        return err;
+    pps = unit->content = unit->content_ref->data;
+
     // Record the current value of pic_init_qp in order to fix up
     // following slices, then overwrite with the global value.
     ctx->current_pic_init_qp = pps->pic_init_qp_minus26 + 26;
@@ -89,7 +98,7 @@ static int h264_redundant_pps_filter(AVBSFContext *bsf, AVPacket *out)
         if (nal->type == H264_NAL_SPS)
             au_has_sps = 1;
         if (nal->type == H264_NAL_PPS) {
-            err = h264_redundant_pps_fixup_pps(ctx, nal->content);
+            err = h264_redundant_pps_fixup_pps(ctx, nal);
             if (err < 0)
                 goto fail;
             if (!au_has_sps) {
@@ -151,7 +160,7 @@ static int h264_redundant_pps_init(AVBSFContext *bsf)
 
         for (i = 0; i < au->nb_units; i++) {
             if (au->units[i].type == H264_NAL_PPS) {
-                err = h264_redundant_pps_fixup_pps(ctx, au->units[i].content);
+                err = h264_redundant_pps_fixup_pps(ctx, &au->units[i]);
                 if (err < 0)
                     goto fail;
             }
-- 
2.19.0



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