mirror of https://github.com/FFmpeg/FFmpeg.git
The packetizer only supports splitting at GOB headers - if such aren't available frequently enough, it splits at any random byte offset (not at a macroblock boundary either, which would be allowed by the spec) and sends a payload header pretend that it starts with a GOB header. As long as a receiver doesn't try to handle such cases cleverly but just drops broken frames, this shouldn't matter too much in practice. Signed-off-by: Martin Storsjö <martin@martin.st>pull/101/head
Thomas Volkert
10 years ago
committed by
Martin Storsjö
parent
adc214e679
commit
a505c0d737
10 changed files with 343 additions and 4 deletions
@ -0,0 +1,202 @@ |
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/*
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* RTP parser for H.261 payload format (RFC 4587) |
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* Copyright (c) 2014 Thomas Volkert <thomas@homer-conferencing.com> |
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* |
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* This file is part of Libav. |
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* |
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* Libav is free software; you can redistribute it and/or |
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* modify it under the terms of the GNU Lesser General Public |
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* License as published by the Free Software Foundation; either |
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* version 2.1 of the License, or (at your option) any later version. |
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* |
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* Libav is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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* Lesser General Public License for more details. |
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* |
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* You should have received a copy of the GNU Lesser General Public |
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* License along with Libav; if not, write to the Free Software |
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
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*/ |
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#include "libavcodec/get_bits.h" |
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#include "avformat.h" |
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#include "rtpdec_formats.h" |
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#define RTP_H261_PAYLOAD_HEADER_SIZE 4 |
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struct PayloadContext { |
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AVIOContext *buf; |
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uint8_t endbyte; |
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int endbyte_bits; |
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uint32_t timestamp; |
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}; |
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static av_cold PayloadContext *h261_new_context(void) |
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{ |
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return av_mallocz(sizeof(PayloadContext)); |
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} |
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static void h261_free_dyn_buffer(AVIOContext **dyn_buf) |
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{ |
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uint8_t *ptr_dyn_buffer; |
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avio_close_dyn_buf(*dyn_buf, &ptr_dyn_buffer); |
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av_free(ptr_dyn_buffer); |
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*dyn_buf = NULL; |
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} |
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static av_cold void h261_free_context(PayloadContext *pl_ctx) |
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{ |
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/* return if context is invalid */ |
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if (!pl_ctx) |
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return; |
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/* free buffer if it is valid */ |
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if (pl_ctx->buf) { |
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h261_free_dyn_buffer(&pl_ctx->buf); |
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} |
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/* free context */ |
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av_free(pl_ctx); |
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} |
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static av_cold int h261_init(AVFormatContext *ctx, int st_index, |
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PayloadContext *data) |
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{ |
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if (st_index < 0) |
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return 0; |
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ctx->streams[st_index]->need_parsing = AVSTREAM_PARSE_FULL; |
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return 0; |
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} |
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static int h261_handle_packet(AVFormatContext *ctx, PayloadContext *rtp_h261_ctx, |
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AVStream *st, AVPacket *pkt, uint32_t *timestamp, |
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const uint8_t *buf, int len, uint16_t seq, |
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int flags) |
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{ |
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int sbit, ebit, gobn, mbap, quant; |
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int res; |
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/* drop data of previous packets in case of non-continuous (lossy) packet stream */ |
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if (rtp_h261_ctx->buf && rtp_h261_ctx->timestamp != *timestamp) { |
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h261_free_dyn_buffer(&rtp_h261_ctx->buf); |
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rtp_h261_ctx->endbyte_bits = 0; |
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} |
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/* sanity check for size of input packet: 1 byte payload at least */ |
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if (len < RTP_H261_PAYLOAD_HEADER_SIZE + 1) { |
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av_log(ctx, AV_LOG_ERROR, "Too short RTP/H.261 packet, got %d bytes\n", len); |
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return AVERROR_INVALIDDATA; |
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} |
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/*
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* decode the H.261 payload header according to section 4.1 of RFC 4587: |
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* (uses 4 bytes between RTP header and H.261 stream per packet) |
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* |
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* 0 1 2 3 |
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* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
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* |SBIT |EBIT |I|V| GOBN | MBAP | QUANT | HMVD | VMVD | |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
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* |
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* Start bit position (SBIT): 3 bits |
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* End bit position (EBIT): 3 bits |
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* INTRA-frame encoded data (I): 1 bit |
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* Motion Vector flag (V): 1 bit |
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* GOB number (GOBN): 4 bits |
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* Macroblock address predictor (MBAP): 5 bits |
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* Quantizer (QUANT): 5 bits |
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* Horizontal motion vector data (HMVD): 5 bits |
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* Vertical motion vector data (VMVD): 5 bits |
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*/ |
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sbit = (buf[0] >> 5) & 0x07; |
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ebit = (buf[0] >> 2) & 0x07; |
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gobn = (buf[1] >> 4) & 0x0f; |
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mbap = ((buf[1] << 1) & 0x1e) | ((buf[2] >> 7) & 0x01); |
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quant = (buf[2] >> 2) & 0x1f; |
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/* pass the H.261 payload header and continue with the actual payload */ |
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buf += RTP_H261_PAYLOAD_HEADER_SIZE; |
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len -= RTP_H261_PAYLOAD_HEADER_SIZE; |
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/* start frame buffering with new dynamic buffer */ |
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if (!rtp_h261_ctx->buf) { |
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/* sanity check: a new frame starts with gobn=0, sbit=0, mbap=0, quant=0 */ |
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if (!gobn && !sbit && !mbap && !quant) { |
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res = avio_open_dyn_buf(&rtp_h261_ctx->buf); |
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if (res < 0) |
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return res; |
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/* update the timestamp in the frame packet with the one from the RTP packet */ |
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rtp_h261_ctx->timestamp = *timestamp; |
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} else { |
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/* frame not started yet, need more packets */ |
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return AVERROR(EAGAIN); |
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} |
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} |
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/* do the "byte merging" at the boundaries of two consecutive frame fragments */ |
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if (rtp_h261_ctx->endbyte_bits || sbit) { |
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if (rtp_h261_ctx->endbyte_bits == sbit) { |
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rtp_h261_ctx->endbyte |= buf[0] & (0xff >> sbit); |
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rtp_h261_ctx->endbyte_bits = 0; |
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buf++; |
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len--; |
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avio_w8(rtp_h261_ctx->buf, rtp_h261_ctx->endbyte); |
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} else { |
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/* ebit/sbit values inconsistent, assuming packet loss */ |
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GetBitContext gb; |
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init_get_bits(&gb, buf, len*8 - ebit); |
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skip_bits(&gb, sbit); |
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if (rtp_h261_ctx->endbyte_bits) { |
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rtp_h261_ctx->endbyte |= get_bits(&gb, 8 - rtp_h261_ctx->endbyte_bits); |
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avio_w8(rtp_h261_ctx->buf, rtp_h261_ctx->endbyte); |
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} |
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while (get_bits_left(&gb) >= 8) |
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avio_w8(rtp_h261_ctx->buf, get_bits(&gb, 8)); |
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rtp_h261_ctx->endbyte_bits = get_bits_left(&gb); |
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if (rtp_h261_ctx->endbyte_bits) |
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rtp_h261_ctx->endbyte = get_bits(&gb, rtp_h261_ctx->endbyte_bits) << |
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(8 - rtp_h261_ctx->endbyte_bits); |
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ebit = 0; |
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len = 0; |
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} |
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} |
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if (ebit) { |
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if (len > 0) |
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avio_write(rtp_h261_ctx->buf, buf, len - 1); |
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rtp_h261_ctx->endbyte_bits = 8 - ebit; |
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rtp_h261_ctx->endbyte = buf[len - 1] & (0xff << ebit); |
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} else { |
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avio_write(rtp_h261_ctx->buf, buf, len); |
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} |
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/* RTP marker bit means: last fragment of current frame was received;
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otherwise, an additional fragment is needed for the current frame */ |
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if (!(flags & RTP_FLAG_MARKER)) |
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return AVERROR(EAGAIN); |
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/* write the completed last byte from the "byte merging" */ |
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if (rtp_h261_ctx->endbyte_bits) |
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avio_w8(rtp_h261_ctx->buf, rtp_h261_ctx->endbyte); |
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rtp_h261_ctx->endbyte_bits = 0; |
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/* close frame buffering and create resulting A/V packet */ |
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res = ff_rtp_finalize_packet(pkt, &rtp_h261_ctx->buf, st->index); |
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if (res < 0) |
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return res; |
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return 0; |
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} |
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RTPDynamicProtocolHandler ff_h261_dynamic_handler = { |
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.enc_name = "H261", |
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.codec_type = AVMEDIA_TYPE_VIDEO, |
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.codec_id = AV_CODEC_ID_H261, |
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.init = h261_init, |
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.alloc = h261_new_context, |
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.free = h261_free_context, |
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.parse_packet = h261_handle_packet, |
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.static_payload_id = 31, |
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}; |
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@ -0,0 +1,102 @@ |
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/*
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* RTP packetization for H.261 video (RFC 4587) |
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* Copyright (c) 2014 Thomas Volkert <thomas@homer-conferencing.com> |
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* |
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* This file is part of Libav. |
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* |
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* Libav is free software; you can redistribute it and/or |
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* modify it under the terms of the GNU Lesser General Public |
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* License as published by the Free Software Foundation; either |
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* version 2.1 of the License, or (at your option) any later version. |
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* |
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* Libav is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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* Lesser General Public License for more details. |
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* |
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* You should have received a copy of the GNU Lesser General Public |
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* License along with Libav; if not, write to the Free Software |
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
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*/ |
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#include "avformat.h" |
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#include "rtpenc.h" |
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#define RTP_H261_HEADER_SIZE 4 |
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static const uint8_t *find_resync_marker_reverse(const uint8_t *restrict start, |
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const uint8_t *restrict end) |
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{ |
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const uint8_t *p = end - 1; |
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start += 1; /* Make sure we never return the original start. */ |
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for (; p > start; p--) { |
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if (p[0] == 0 && p[1] == 1) |
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return p; |
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} |
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return end; |
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} |
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void ff_rtp_send_h261(AVFormatContext *ctx, const uint8_t *frame_buf, int frame_size) |
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{ |
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int cur_frame_size; |
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int last_packet_of_frame; |
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RTPMuxContext *rtp_ctx = ctx->priv_data; |
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/* use the default 90 KHz time stamp */ |
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rtp_ctx->timestamp = rtp_ctx->cur_timestamp; |
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/* continue as long as not all frame data is processed */ |
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while (frame_size > 0) { |
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/*
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* encode the H.261 payload header according to section 4.1 of RFC 4587: |
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* (uses 4 bytes between RTP header and H.261 stream per packet) |
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* |
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* 0 1 2 3 |
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* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
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* |SBIT |EBIT |I|V| GOBN | MBAP | QUANT | HMVD | VMVD | |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
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* |
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* Start bit position (SBIT): 3 bits |
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* End bit position (EBIT): 3 bits |
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* INTRA-frame encoded data (I): 1 bit |
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* Motion Vector flag (V): 1 bit |
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* GOB number (GOBN): 4 bits |
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* Macroblock address predictor (MBAP): 5 bits |
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* Quantizer (QUANT): 5 bits |
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* Horizontal motion vector data (HMVD): 5 bits |
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* Vertical motion vector data (VMVD): 5 bits |
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*/ |
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rtp_ctx->buf[0] = 1; /* sbit=0, ebit=0, i=0, v=1 */ |
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rtp_ctx->buf[1] = 0; /* gobn=0, mbap=0 */ |
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rtp_ctx->buf[2] = 0; /* quant=0, hmvd=5 */ |
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rtp_ctx->buf[3] = 0; /* vmvd=0 */ |
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if (frame_size < 2 || frame_buf[0] != 0 || frame_buf[1] != 1) { |
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/* A full, correct fix for this would be to make the H261 encoder
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* support inserting extra GOB headers (triggered by setting e.g. |
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* "-ps 1"), and including information about macroblock boundaries |
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* (such as for h263_rfc2190). */ |
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av_log(ctx, AV_LOG_WARNING, |
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"RTP/H261 packet not cut at a GOB boundary, not signaled correctly\n"); |
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} |
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cur_frame_size = FFMIN(rtp_ctx->max_payload_size - RTP_H261_HEADER_SIZE, frame_size); |
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/* look for a better place to split the frame into packets */ |
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if (cur_frame_size < frame_size) { |
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const uint8_t *packet_end = find_resync_marker_reverse(frame_buf, |
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frame_buf + cur_frame_size); |
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cur_frame_size = packet_end - frame_buf; |
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} |
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/* calculate the "marker" bit for the RTP header */ |
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last_packet_of_frame = cur_frame_size == frame_size; |
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/* complete and send RTP packet */ |
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memcpy(&rtp_ctx->buf[RTP_H261_HEADER_SIZE], frame_buf, cur_frame_size); |
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ff_rtp_send_data(ctx, rtp_ctx->buf, RTP_H261_HEADER_SIZE + cur_frame_size, last_packet_of_frame); |
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frame_buf += cur_frame_size; |
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frame_size -= cur_frame_size; |
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} |
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} |
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Reference in new issue