avcodec/pthread_frame, decode: allow errors to happen on draining

So, all frames and errors are correctly reported in order.
Also limit the numbers of error during draining to prevent infinite loop.

This fix fate failure with THREADS>=4:
  make fate-h264-attachment-631 THREADS=4
This also reverts a755b725ec1d657609c8bd726ce37e7cf193d03f.

Suggested-by: wm4, Ronald S. Bultje, Marton Balint
Reviewed-by: w4 <nfxjfg@googlemail.com>
Reviewed-by: Ronald S. Bultje <rsbultje@gmail.com>
Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: Muhammad Faiz <mfcc64@gmail.com>

1 files changed, 19 insertions, 2 deletions

diff --git a/libavcodec/decode.c b/libavcodec/decode.c
index 6ff3c401ba..edfae5583c 100644
--- a/libavcodec/decode.c
+++ b/libavcodec/decode.c
@@ -568,8 +568,24 @@ FF_ENABLE_DEPRECATION_WARNINGS
         avctx->time_base = av_inv_q(av_mul_q(avctx->framerate, (AVRational){avctx->ticks_per_frame, 1}));
 #endif
 
-    if (avctx->internal->draining && !got_frame)
-        avci->draining_done = 1;
+    /* do not stop draining when got_frame != 0 or ret < 0 */
+    if (avctx->internal->draining && !got_frame) {
+        if (ret < 0) {
+            /* prevent infinite loop if a decoder wrongly always return error on draining */
+            /* reasonable nb_errors_max = maximum b frames + thread count */
+            int nb_errors_max = 20 + (HAVE_THREADS && avctx->active_thread_type & FF_THREAD_FRAME ?
+                                avctx->thread_count : 1);
+
+            if (avci->nb_draining_errors++ >= nb_errors_max) {
+                av_log(avctx, AV_LOG_ERROR, "Too many errors when draining, this is a bug. "
+                       "Stop draining and force EOF.\n");
+                avci->draining_done = 1;
+                ret = AVERROR_BUG;
+            }
+        } else {
+            avci->draining_done = 1;
+        }
+    }
 
     avci->compat_decode_consumed += ret;
 
@@ -1659,6 +1675,7 @@ void avcodec_flush_buffers(AVCodecContext *avctx)
 {
     avctx->internal->draining      = 0;
     avctx->internal->draining_done = 0;
+    avctx->internal->nb_draining_errors = 0;
     av_frame_unref(avctx->internal->buffer_frame);
     av_frame_unref(avctx->internal->compat_decode_frame);
     av_packet_unref(avctx->internal->buffer_pkt);