| Line | Branch | Exec | Source |
|---|---|---|---|
| 1 | /* | ||
| 2 | * RTP packetization for H.261 video (RFC 4587) | ||
| 3 | * Copyright (c) 2014 Thomas Volkert <thomas@homer-conferencing.com> | ||
| 4 | * | ||
| 5 | * This file is part of FFmpeg. | ||
| 6 | * | ||
| 7 | * FFmpeg is free software; you can redistribute it and/or | ||
| 8 | * modify it under the terms of the GNU Lesser General Public | ||
| 9 | * License as published by the Free Software Foundation; either | ||
| 10 | * version 2.1 of the License, or (at your option) any later version. | ||
| 11 | * | ||
| 12 | * FFmpeg is distributed in the hope that it will be useful, | ||
| 13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
| 14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | ||
| 15 | * Lesser General Public License for more details. | ||
| 16 | * | ||
| 17 | * You should have received a copy of the GNU Lesser General Public | ||
| 18 | * License along with FFmpeg; if not, write to the Free Software | ||
| 19 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | ||
| 20 | */ | ||
| 21 | |||
| 22 | #include "avformat.h" | ||
| 23 | #include "rtpenc.h" | ||
| 24 | |||
| 25 | #define RTP_H261_HEADER_SIZE 4 | ||
| 26 | |||
| 27 | ✗ | static const uint8_t *find_resync_marker_reverse(const uint8_t *restrict start, | |
| 28 | const uint8_t *restrict end) | ||
| 29 | { | ||
| 30 | ✗ | const uint8_t *p = end - 1; | |
| 31 | ✗ | start += 1; /* Make sure we never return the original start. */ | |
| 32 | ✗ | for (; p > start; p--) { | |
| 33 | ✗ | if (p[0] == 0 && p[1] == 1) | |
| 34 | ✗ | return p; | |
| 35 | } | ||
| 36 | ✗ | return end; | |
| 37 | } | ||
| 38 | |||
| 39 | ✗ | void ff_rtp_send_h261(AVFormatContext *ctx, const uint8_t *frame_buf, int frame_size) | |
| 40 | { | ||
| 41 | int cur_frame_size; | ||
| 42 | int last_packet_of_frame; | ||
| 43 | ✗ | RTPMuxContext *rtp_ctx = ctx->priv_data; | |
| 44 | |||
| 45 | /* use the default 90 KHz time stamp */ | ||
| 46 | ✗ | rtp_ctx->timestamp = rtp_ctx->cur_timestamp; | |
| 47 | |||
| 48 | /* continue as long as not all frame data is processed */ | ||
| 49 | ✗ | while (frame_size > 0) { | |
| 50 | /* | ||
| 51 | * encode the H.261 payload header according to section 4.1 of RFC 4587: | ||
| 52 | * (uses 4 bytes between RTP header and H.261 stream per packet) | ||
| 53 | * | ||
| 54 | * 0 1 2 3 | ||
| 55 | * 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 | ||
| 56 | * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ||
| 57 | * |SBIT |EBIT |I|V| GOBN | MBAP | QUANT | HMVD | VMVD | | ||
| 58 | * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ||
| 59 | * | ||
| 60 | * Start bit position (SBIT): 3 bits | ||
| 61 | * End bit position (EBIT): 3 bits | ||
| 62 | * INTRA-frame encoded data (I): 1 bit | ||
| 63 | * Motion Vector flag (V): 1 bit | ||
| 64 | * GOB number (GOBN): 4 bits | ||
| 65 | * Macroblock address predictor (MBAP): 5 bits | ||
| 66 | * Quantizer (QUANT): 5 bits | ||
| 67 | * Horizontal motion vector data (HMVD): 5 bits | ||
| 68 | * Vertical motion vector data (VMVD): 5 bits | ||
| 69 | */ | ||
| 70 | ✗ | rtp_ctx->buf[0] = 1; /* sbit=0, ebit=0, i=0, v=1 */ | |
| 71 | ✗ | rtp_ctx->buf[1] = 0; /* gobn=0, mbap=0 */ | |
| 72 | ✗ | rtp_ctx->buf[2] = 0; /* quant=0, hmvd=5 */ | |
| 73 | ✗ | rtp_ctx->buf[3] = 0; /* vmvd=0 */ | |
| 74 | ✗ | if (frame_size < 2 || frame_buf[0] != 0 || frame_buf[1] != 1) { | |
| 75 | /* A full, correct fix for this would be to make the H.261 encoder | ||
| 76 | * support inserting extra GOB headers (triggered by setting e.g. | ||
| 77 | * "-ps 1"), and including information about macroblock boundaries | ||
| 78 | * (such as for h263_rfc2190). */ | ||
| 79 | ✗ | av_log(ctx, AV_LOG_WARNING, | |
| 80 | "RTP/H.261 packet not cut at a GOB boundary, not signaled correctly\n"); | ||
| 81 | } | ||
| 82 | |||
| 83 | ✗ | cur_frame_size = FFMIN(rtp_ctx->max_payload_size - RTP_H261_HEADER_SIZE, frame_size); | |
| 84 | |||
| 85 | /* look for a better place to split the frame into packets */ | ||
| 86 | ✗ | if (cur_frame_size < frame_size) { | |
| 87 | ✗ | const uint8_t *packet_end = find_resync_marker_reverse(frame_buf, | |
| 88 | frame_buf + cur_frame_size); | ||
| 89 | ✗ | cur_frame_size = packet_end - frame_buf; | |
| 90 | } | ||
| 91 | |||
| 92 | /* calculate the "marker" bit for the RTP header */ | ||
| 93 | ✗ | last_packet_of_frame = cur_frame_size == frame_size; | |
| 94 | |||
| 95 | /* complete and send RTP packet */ | ||
| 96 | ✗ | memcpy(&rtp_ctx->buf[RTP_H261_HEADER_SIZE], frame_buf, cur_frame_size); | |
| 97 | ✗ | ff_rtp_send_data(ctx, rtp_ctx->buf, RTP_H261_HEADER_SIZE + cur_frame_size, last_packet_of_frame); | |
| 98 | |||
| 99 | ✗ | frame_buf += cur_frame_size; | |
| 100 | ✗ | frame_size -= cur_frame_size; | |
| 101 | } | ||
| 102 | ✗ | } | |
| 103 |