media/video: remove workaround for h263p

This commit adds a patch from libav resolving issues with h263p encoder.
see https://bugzilla.libav.org/show_bug.cgi?id=912

Change-Id: I95f5e81063af01a57be47b70fadaf54c3393eb52
Tuleap: #138

contrib/src/libav/0004-mpegvideo_enc-enable-rtp_mode-when-multiple-slices-a.patch

+From f6c94457b44f41d900cd0991857f54e1f0ccedd6 Mon Sep 17 00:00:00 2001
+From: Anton Khirnov <anton@khirnov.net>
+Date: Wed, 18 Nov 2015 10:37:16 +0100
+Subject: [PATCH] mpegvideo_enc: enable rtp_mode when multiple slices are used
+
+Currently, multiple slices with just one thread produce corrupted
+output.
+
+Additionally, enable slice structured mode for h263(+)
+
+Bug-Id: 912
+CC: libav-stabl@libav.org
+---
+ libavcodec/mpegvideo_enc.c | 10 +++++++---
+ 1 file changed, 7 insertions(+), 3 deletions(-)
+
+diff --git a/libavcodec/mpegvideo_enc.c b/libavcodec/mpegvideo_enc.c
+index d572b85..b915741 100644
+--- a/libavcodec/mpegvideo_enc.c
++++ b/libavcodec/mpegvideo_enc.c
+@@ -519,9 +519,6 @@ FF_ENABLE_DEPRECATION_WARNINGS
+         return -1;
+     }
+
+-    if (s->avctx->thread_count > 1)
+-        s->rtp_mode = 1;
+-
+     if (!avctx->time_base.den || !avctx->time_base.num) {
+         av_log(avctx, AV_LOG_ERROR, "framerate not set\n");
+         return -1;
+@@ -764,6 +761,13 @@ FF_ENABLE_DEPRECATION_WARNINGS
+     if ((CONFIG_H263P_ENCODER || CONFIG_RV20_ENCODER) && s->modified_quant)
+         s->chroma_qscale_table = ff_h263_chroma_qscale_table;
+
++    if (s->slice_context_count > 1) {
++        s->rtp_mode = 1;
++
++        if (avctx->codec_id == AV_CODEC_ID_H263 || avctx->codec_id == AV_CODEC_ID_H263P)
++            s->h263_slice_structured = 1;
++    }
++
+     s->quant_precision = 5;
+
+     ff_set_cmp(&s->mecc, s->mecc.ildct_cmp,      s->avctx->ildct_cmp);
+--
+2.1.4

contrib/src/libav/rules.mak

@@ -186,6 +186,7 @@ libav: libav-$(LIBAV_HASH).tar.xz .sum-libav
 	$(APPLY) $(SRC)/libav/0001-rtpdec-add-a-trace-when-jitter-buffer-is-full.patch
 	$(APPLY) $(SRC)/libav/0002-rtpdec-inform-jitter-buffer-size.patch
 	$(APPLY) $(SRC)/libav/0003-rtsp-warning-when-max_delay-reached.patch
+	$(APPLY) $(SRC)/libav/0004-mpegvideo_enc-enable-rtp_mode-when-multiple-slices-a.patch
 	$(MOVE)
 
 .libav: libav

src/media/media_encoder.cpp

@@ -201,10 +201,6 @@ MediaEncoder::openOutput(const char *filename,
     } else if (args.codec->systemCodecInfo.avcodecId == AV_CODEC_ID_H263) {
         encoderCtx_->bit_rate = encoderCtx_->rc_max_rate =  maxBitrate;
         encoderCtx_->rc_buffer_size = maxBitrate;
-        // on libav there are video artifcats if multithreading is enabled
-        // see https://bugzilla.libav.org/show_bug.cgi?id=912
-        // TODO: this is a workaround !
-        encoderCtx_->thread_count = 1;
         RING_DBG("Using Max bitrate %d", maxBitrate);
     }