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FFmpeg/libavformat/rtpdec_vp8.c
Martin Storsjö 76c40fbef0 rtpdec_vp8: Don't trim too much data from broken frames 
Previously, for broken frames, we only returned the first partition
of the frame (we would append all the received packets to the packet
buffer, then set pkt->size to the size of the first partition, since
the rest of the frame could have lost data inbetween) - now instead
return the full buffered data we have, but don't append anything more
to the buffer after the lost packet discontinuity. Decoding the
truncated packet should hopefully get better quality than trimming out
everything after the first partition.

Signed-off-by: Martin Storsjö <martin@martin.st>
2013-01-10 09:43:01 +02:00

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/*
* RTP VP8 Depacketizer
* Copyright (c) 2010 Josh Allmann
* Copyright (c) 2012 Martin Storsjo
*
* This file is part of Libav.
*
* Libav 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.
*
* Libav 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 Libav; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
/**
* @file
* @brief RTP support for the VP8 payload
* @author Josh Allmann <joshua.allmann@gmail.com>
* @see http://tools.ietf.org/html/draft-ietf-payload-vp8-05
*/
#include "libavcodec/bytestream.h"
#include "rtpdec_formats.h"
struct PayloadContext {
AVIOContext *data;
uint32_t timestamp;
int is_keyframe;
/* If sequence_ok is set, we keep returning data (even if we might have
* lost some data, but we haven't lost any too critical data that would
* cause the decoder to desynchronize and output random garbage).
*/
int sequence_ok;
int first_part_size;
uint16_t prev_seq;
int prev_pictureid;
int broken_frame;
/* If sequence_dirty is set, we have lost some data (critical or
* non-critical) and decoding will have some sort of artefacts, and
* we thus should request a new keyframe.
*/
int sequence_dirty;
int got_keyframe;
};
static void vp8_free_buffer(PayloadContext *vp8)
{
uint8_t *tmp;
if (!vp8->data)
return;
avio_close_dyn_buf(vp8->data, &tmp);
av_free(tmp);
vp8->data = NULL;
}
static int vp8_broken_sequence(AVFormatContext *ctx, PayloadContext *vp8,
const char *msg)
{
vp8->sequence_ok = 0;
av_log(ctx, AV_LOG_WARNING, "%s", msg);
vp8_free_buffer(vp8);
return AVERROR(EAGAIN);
}
static int vp8_handle_packet(AVFormatContext *ctx, PayloadContext *vp8,
AVStream *st, AVPacket *pkt, uint32_t *timestamp,
const uint8_t *buf, int len, uint16_t seq,
int flags)
{
int start_partition, end_packet;
int extended_bits, part_id;
int pictureid_present = 0, tl0picidx_present = 0, tid_present = 0,
keyidx_present = 0;
int pictureid = -1, pictureid_mask = 0;
int returned_old_frame = 0;
uint32_t old_timestamp;
if (!buf) {
if (vp8->data) {
int ret = ff_rtp_finalize_packet(pkt, &vp8->data, st->index);
if (ret < 0)
return ret;
*timestamp = vp8->timestamp;
if (vp8->sequence_dirty)
pkt->flags |= AV_PKT_FLAG_CORRUPT;
return 0;
}
return AVERROR(EAGAIN);
}
if (len < 1)
return AVERROR_INVALIDDATA;
extended_bits = buf[0] & 0x80;
start_partition = buf[0] & 0x10;
part_id = buf[0] & 0x0f;
end_packet = flags & RTP_FLAG_MARKER;
buf++;
len--;
if (extended_bits) {
if (len < 1)
return AVERROR_INVALIDDATA;
pictureid_present = buf[0] & 0x80;
tl0picidx_present = buf[0] & 0x40;
tid_present = buf[0] & 0x20;
keyidx_present = buf[0] & 0x10;
buf++;
len--;
}
if (pictureid_present) {
if (len < 1)
return AVERROR_INVALIDDATA;
if (buf[0] & 0x80) {
if (len < 2)
return AVERROR_INVALIDDATA;
pictureid = AV_RB16(buf) & 0x7fff;
pictureid_mask = 0x7fff;
buf += 2;
len -= 2;
} else {
pictureid = buf[0] & 0x7f;
pictureid_mask = 0x7f;
buf++;
len--;
}
}
if (tl0picidx_present) {
// Ignoring temporal level zero index
buf++;
len--;
}
if (tid_present || keyidx_present) {
// Ignoring temporal layer index, layer sync bit and keyframe index
buf++;
len--;
}
if (len < 1)
return AVERROR_INVALIDDATA;
if (start_partition && part_id == 0 && len >= 3) {
int res;
int non_key = buf[0] & 0x01;
if (!non_key) {
vp8_free_buffer(vp8);
// Keyframe, decoding ok again
vp8->sequence_ok = 1;
vp8->sequence_dirty = 0;
vp8->got_keyframe = 1;
} else {
int can_continue = vp8->data && !vp8->is_keyframe &&
avio_tell(vp8->data) >= vp8->first_part_size;
if (!vp8->sequence_ok)
return AVERROR(EAGAIN);
if (!vp8->got_keyframe)
return vp8_broken_sequence(ctx, vp8, "Keyframe missing\n");
if (pictureid >= 0) {
if (pictureid != ((vp8->prev_pictureid + 1) & pictureid_mask)) {
return vp8_broken_sequence(ctx, vp8,
"Missed a picture, sequence broken\n");
} else {
if (vp8->data && !can_continue)
return vp8_broken_sequence(ctx, vp8,
"Missed a picture, sequence broken\n");
}
} else {
uint16_t expected_seq = vp8->prev_seq + 1;
int16_t diff = seq - expected_seq;
if (vp8->data) {
// No picture id, so we can't know if missed packets
// contained any new frames. If diff == 0, we did get
// later packets from the same frame (matching timestamp),
// so we know we didn't miss any frame. If diff == 1 and
// we still have data (not flushed by the end of frame
// marker), the single missed packet must have been part
// of the same frame.
if ((diff == 0 || diff == 1) && can_continue) {
// Proceed with what we have
} else {
return vp8_broken_sequence(ctx, vp8,
"Missed too much, sequence broken\n");
}
} else {
if (diff != 0)
return vp8_broken_sequence(ctx, vp8,
"Missed unknown data, sequence broken\n");
}
}
if (vp8->data) {
vp8->sequence_dirty = 1;
if (avio_tell(vp8->data) >= vp8->first_part_size) {
int ret = ff_rtp_finalize_packet(pkt, &vp8->data, st->index);
if (ret < 0)
return ret;
pkt->flags |= AV_PKT_FLAG_CORRUPT;
returned_old_frame = 1;
old_timestamp = vp8->timestamp;
} else {
// Shouldn't happen
vp8_free_buffer(vp8);
}
}
}
vp8->first_part_size = (AV_RL16(&buf[1]) << 3 | buf[0] >> 5) + 3;
if ((res = avio_open_dyn_buf(&vp8->data)) < 0)
return res;
vp8->timestamp = *timestamp;
vp8->broken_frame = 0;
vp8->prev_pictureid = pictureid;
vp8->is_keyframe = !non_key;
} else {
uint16_t expected_seq = vp8->prev_seq + 1;
if (!vp8->sequence_ok)
return AVERROR(EAGAIN);
if (vp8->timestamp != *timestamp) {
// Missed the start of the new frame, sequence broken
return vp8_broken_sequence(ctx, vp8,
"Received no start marker; dropping frame\n");
}
if (seq != expected_seq) {
if (vp8->is_keyframe) {
return vp8_broken_sequence(ctx, vp8,
"Missed part of a keyframe, sequence broken\n");
} else if (vp8->data && avio_tell(vp8->data) >= vp8->first_part_size) {
vp8->broken_frame = 1;
vp8->sequence_dirty = 1;
} else {
return vp8_broken_sequence(ctx, vp8,
"Missed part of the first partition, sequence broken\n");
}
}
}
if (!vp8->data)
return vp8_broken_sequence(ctx, vp8, "Received no start marker\n");
vp8->prev_seq = seq;
if (!vp8->broken_frame)
avio_write(vp8->data, buf, len);
if (returned_old_frame) {
*timestamp = old_timestamp;
return end_packet ? 1 : 0;
}
if (end_packet) {
int ret;
ret = ff_rtp_finalize_packet(pkt, &vp8->data, st->index);
if (ret < 0)
return ret;
if (vp8->sequence_dirty)
pkt->flags |= AV_PKT_FLAG_CORRUPT;
return 0;
}
return AVERROR(EAGAIN);
}
static PayloadContext *vp8_new_context(void)
{
PayloadContext *vp8 = av_mallocz(sizeof(PayloadContext));
if (!vp8)
return NULL;
vp8->sequence_ok = 1;
return vp8;
}
static void vp8_free_context(PayloadContext *vp8)
{
vp8_free_buffer(vp8);
av_free(vp8);
}
static int vp8_need_keyframe(PayloadContext *vp8)
{
return vp8->sequence_dirty || !vp8->sequence_ok;
}
RTPDynamicProtocolHandler ff_vp8_dynamic_handler = {
.enc_name = "VP8",
.codec_type = AVMEDIA_TYPE_VIDEO,
.codec_id = AV_CODEC_ID_VP8,
.alloc = vp8_new_context,
.free = vp8_free_context,
.parse_packet = vp8_handle_packet,
.need_keyframe = vp8_need_keyframe,
};
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