On 30 July 2010 00:22, Martin Storsjö <[email protected]> wrote:
> On Thu, 29 Jul 2010, Josh Allmann wrote:
>
>> Here is a packetizer and a depacketizer for VP8 RTP.
>>
>> Playback is only semi-smooth; it drops way too many frames. The
>> depacketizer likes to claim it gets an extra packet after the
>> frame-end (which is typically one byte smaller than the actual
>> frame-end packet). Still a work in progress.
>
> Didn't feel any significant frame dropping here (btw, if playing with
> ffplay, make sure you use -noframedrop, sometimes ffplay constantly feels
> it's behind and needs to drop some frames to catch up, but since the
> source is realtime, it still has to block for more frames, so it
> constantly drops frames), but the playback console is spammed with
> messages like this:
>
> [vp8 @ 0x10188fe00] Unknown profile 6
> [vp8 @ 0x10188fe00] Header size larger than data provided
> [rtsp @ 0x10202dc00] Received no start marker; dropping frame
>

-noframedrop helped, but the last message is what I am concerned with;
it really should not happen. Those seem like phantom packets.

> In general, this looks quite ok (I haven't read the spec, but from the
> code it looks quite simple), here's a quick initial review:
>

It is basically raw RTP with the addition of two bits, one to mark
keyframes, and another to mark the start of a frame. I made a few
assumptions here that were not covered by the spec:*

-Those bits are located at the first byte prior to the data payload.
-The sdp rtpmap codec ID is "VP8."

*https://groups.google.com/a/webmproject.org/group/webm-discuss/browse_thread/thread/550f946b0e22ead2#

>> +    keyframe = ( !(*buf & 1) ) << 3;
>> +
>
> I guess this could be written a little less convoluted as
>
> keyframe = *buf & 1 ? 0 : 8;
>
> but that's mostly bikeshedding. :-)
>

Fixed, since it is clearer that way.

>> +    *s->buf_ptr++ = keyframe | 4; // 0b100 indicates start of frame
>> +    while (size > 0) {
>> +        len = size > max_packet_size ? max_packet_size : size;
>
> len = FFMIN(size, max_packet_size);
>

Fixed


>> +    int start_packet    = *buf & 4;
>> +    int end_packet      = flags & RTP_FLAG_MARKER;
>> +    int is_keyframe     = *buf & 8;
>
> Keep in mind that buf can be NULL
>

Fixed.

Josh
From 226b27d1f0b91b602e20518f5d1b40125a6d02a5 Mon Sep 17 00:00:00 2001
From: Josh Allmann <[email protected]>
Date: Wed, 28 Jul 2010 00:30:09 -0700
Subject: [PATCH 1/2] Add RTP packetization of VP8.

---
 libavformat/rtpenc.c |   27 +++++++++++++++++++++++++++
 libavformat/sdp.c    |    4 ++++
 2 files changed, 31 insertions(+), 0 deletions(-)

diff --git a/libavformat/rtpenc.c b/libavformat/rtpenc.c
index 4453f65..78ced13 100644
--- a/libavformat/rtpenc.c
+++ b/libavformat/rtpenc.c
@@ -53,6 +53,7 @@ static int is_supported(enum CodecID id)
     case CODEC_ID_MPEG2TS:
     case CODEC_ID_AMR_NB:
     case CODEC_ID_AMR_WB:
+    case CODEC_ID_VP8:
         return 1;
     default:
         return 0;
@@ -291,6 +292,30 @@ static void rtp_send_mpegaudio(AVFormatContext *s1,
     }
 }
 
+static void rtp_send_vp8(AVFormatContext *s1, const uint8_t *buf, int size)
+{
+    RTPMuxContext *s = s1->priv_data;
+    int len, max_packet_size, keyframe;
+
+    s->buf_ptr = s->buf;
+    s->timestamp = s->cur_timestamp;
+    max_packet_size = s->max_payload_size - 1; // minus one for header byte
+    keyframe = *buf & 1 ? 0 : 8; // 0b1000 indicates keyframe
+
+    *s->buf_ptr++ = keyframe | 4; // 0b100 indicates start of frame
+    while (size > 0) {
+        len = FFMIN(size, max_packet_size);
+
+        memcpy(s->buf_ptr, buf, len);
+        ff_rtp_send_data(s1, s->buf, len+1, size == len); // marker bit is last packet in frame
+
+        size -= len;
+        buf += len;
+        s->buf_ptr = s->buf;
+        *s->buf_ptr++ = keyframe;
+    }
+}
+
 static void rtp_send_raw(AVFormatContext *s1,
                          const uint8_t *buf1, int size)
 {
@@ -393,6 +418,8 @@ static int rtp_write_packet(AVFormatContext *s1, AVPacket *pkt)
     case CODEC_ID_H263P:
         ff_rtp_send_h263(s1, pkt->data, size);
         break;
+    case CODEC_ID_VP8:
+        rtp_send_vp8(s1, pkt->data, size);
     default:
         /* better than nothing : send the codec raw data */
         rtp_send_raw(s1, pkt->data, size);
diff --git a/libavformat/sdp.c b/libavformat/sdp.c
index b34b944..a7a3c13 100644
--- a/libavformat/sdp.c
+++ b/libavformat/sdp.c
@@ -297,6 +297,10 @@ static char *sdp_write_media_attributes(char *buff, int size, AVCodecContext *c,
                                      payload_type, c->sample_rate, c->channels,
                                      payload_type);
             break;
+        case CODEC_ID_VP8:
+            av_strlcatf(buff, size, "a=rtpmap:%d VP8/90000\r\n",
+                                     payload_type);
+            break;
         default:
             /* Nothing special to do here... */
             break;
-- 
1.7.0.4

From 49859ad2bc3d2a9ea3e25b2e33edb536b08d3714 Mon Sep 17 00:00:00 2001
From: Josh Allmann <[email protected]>
Date: Thu, 29 Jul 2010 03:51:36 -0700
Subject: [PATCH 2/2] Add RTP depacketization of VP8.

---
 libavformat/Makefile     |    1 +
 libavformat/rtpdec.c     |    2 +
 libavformat/rtpdec_vp8.c |  103 ++++++++++++++++++++++++++++++++++++++++++++++
 libavformat/rtpdec_vp8.h |   29 +++++++++++++
 4 files changed, 135 insertions(+), 0 deletions(-)
 create mode 100644 libavformat/rtpdec_vp8.c
 create mode 100644 libavformat/rtpdec_vp8.h

diff --git a/libavformat/Makefile b/libavformat/Makefile
index c32a254..fa4f233 100644
--- a/libavformat/Makefile
+++ b/libavformat/Makefile
@@ -233,6 +233,7 @@ OBJS-$(CONFIG_SDP_DEMUXER)               += rtsp.o        \
                                             rtpdec_mpeg4.o \
                                             rtpdec_qdm2.o \
                                             rtpdec_svq3.o \
+                                            rtpdec_vp8.o  \
                                             rtpdec_xiph.o
 OBJS-$(CONFIG_SEGAFILM_DEMUXER)          += segafilm.o
 OBJS-$(CONFIG_SHORTEN_DEMUXER)           += raw.o
diff --git a/libavformat/rtpdec.c b/libavformat/rtpdec.c
index 0e2aebb..c1ec21d 100644
--- a/libavformat/rtpdec.c
+++ b/libavformat/rtpdec.c
@@ -37,6 +37,7 @@
 #include "rtpdec_mpeg4.h"
 #include "rtpdec_qdm2.h"
 #include "rtpdec_svq3.h"
+#include "rtpdec_vp8.h"
 #include "rtpdec_xiph.h"
 
 //#define DEBUG
@@ -72,6 +73,7 @@ void av_register_rtp_dynamic_payload_handlers(void)
     ff_register_dynamic_payload_handler(&ff_theora_dynamic_handler);
     ff_register_dynamic_payload_handler(&ff_qdm2_dynamic_handler);
     ff_register_dynamic_payload_handler(&ff_svq3_dynamic_handler);
+    ff_register_dynamic_payload_handler(&ff_vp8_dynamic_handler);
 
     ff_register_dynamic_payload_handler(&ff_ms_rtp_asf_pfv_handler);
     ff_register_dynamic_payload_handler(&ff_ms_rtp_asf_pfa_handler);
diff --git a/libavformat/rtpdec_vp8.c b/libavformat/rtpdec_vp8.c
new file mode 100644
index 0000000..2bd01fe
--- /dev/null
+++ b/libavformat/rtpdec_vp8.c
@@ -0,0 +1,103 @@
+/*
+ * RTP VP8 Depacketizer
+ * Copyright (c) 2010 Josh Allmann
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "rtpdec_vp8.h"
+
+struct PayloadContext {
+    ByteIOContext *data;
+    int            is_keyframe; // this is rather unused
+};
+
+static int vp8_handle_packet(AVFormatContext *ctx,
+                             PayloadContext *vp8,
+                             AVStream *st,
+                             AVPacket *pkt,
+                             uint32_t *timestamp,
+                             const uint8_t *buf,
+                             int len, int flags)
+{
+    int start_packet, end_packet, is_keyframe;
+
+    if (!buf)
+        return AVERROR_INVALIDDATA;
+
+    start_packet    = *buf & 4;
+    end_packet      = flags & RTP_FLAG_MARKER;
+    is_keyframe     = *buf & 8;
+    buf++;
+    len--;
+
+    if (start_packet) {
+        int res;
+        if (vp8->data) { // drop old frame
+            uint8_t *tmp;
+            url_close_dyn_buf(vp8->data, &tmp);
+            vp8->data = NULL;
+            av_free(tmp);
+        }
+        if ((res = url_open_dyn_buf(&vp8->data)) < 0)
+            return res;
+        vp8->is_keyframe = is_keyframe;
+    }
+
+    if (!vp8->data) {
+        av_log(ctx, AV_LOG_WARNING,
+               "Received no start marker; dropping frame\n");
+        return AVERROR(EAGAIN);
+    }
+
+    put_buffer(vp8->data, buf, len);
+
+    if (end_packet) {
+        av_init_packet(pkt);
+        pkt->stream_index = st->index;
+        pkt->size = url_close_dyn_buf(vp8->data, &pkt->data);
+        pkt->destruct = av_destruct_packet;
+        vp8->data = NULL;
+        return 0;
+    }
+
+    return AVERROR(EAGAIN);
+}
+
+static PayloadContext *vp8_new_context(void)
+{
+    return av_mallocz(sizeof(PayloadContext));
+}
+
+static void vp8_free_context(PayloadContext *vp8)
+{
+    if (vp8->data) {
+        uint8_t *tmp;
+        url_close_dyn_buf(vp8->data, &tmp);
+        av_free(tmp);
+    }
+    av_free(vp8);
+}
+
+RTPDynamicProtocolHandler ff_vp8_dynamic_handler = {
+    .enc_name       = "VP8",
+    .codec_type     = AVMEDIA_TYPE_VIDEO,
+    .codec_id       = CODEC_ID_VP8,
+    .open           = vp8_new_context,
+    .close          = vp8_free_context,
+    .parse_packet   = vp8_handle_packet,
+};
diff --git a/libavformat/rtpdec_vp8.h b/libavformat/rtpdec_vp8.h
new file mode 100644
index 0000000..f19ecfa
--- /dev/null
+++ b/libavformat/rtpdec_vp8.h
@@ -0,0 +1,29 @@
+/*
+ * RTP VP8 Protocol
+ * Copyright (c) 2010 Josh Allmann
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef AVFORMAT_RTPDEC_VP8_H
+#define AVFORMAT_RTPDEC_VP8_H
+
+#include "rtpdec.h"
+
+extern RTPDynamicProtocolHandler ff_vp8_dynamic_handler;
+
+#endif /* AVFORMAT_RTPDEC_VP8_H */
-- 
1.7.0.4

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