1/* 2 * RTP H.263 Depacketizer, RFC 4629 3 * Copyright (c) 2010 Martin Storsjo 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 "rtpdec_formats.h" 24#include "libavutil/attributes.h" 25#include "libavutil/intreadwrite.h" 26 27static av_cold int h263_init(AVFormatContext *ctx, int st_index, 28 PayloadContext *data) 29{ 30 if (st_index < 0) 31 return 0; 32 ctx->streams[st_index]->need_parsing = AVSTREAM_PARSE_FULL; 33 return 0; 34} 35 36int ff_h263_handle_packet(AVFormatContext *ctx, PayloadContext *data, 37 AVStream *st, AVPacket *pkt, uint32_t *timestamp, 38 const uint8_t *buf, int len, uint16_t seq, int flags) 39{ 40 uint8_t *ptr; 41 uint16_t header; 42 int startcode, vrc, picture_header; 43 44 if (len < 2) { 45 av_log(ctx, AV_LOG_ERROR, "Too short H.263 RTP packet\n"); 46 return AVERROR_INVALIDDATA; 47 } 48 49 /* Decode the 16 bit H.263+ payload header, as described in section 50 * 5.1 of RFC 4629. The fields of this header are: 51 * - 5 reserved bits, should be ignored. 52 * - One bit (P, startcode), indicating a picture start, picture segment 53 * start or video sequence end. If set, two zero bytes should be 54 * prepended to the payload. 55 * - One bit (V, vrc), indicating the presence of an 8 bit Video 56 * Redundancy Coding field after this 16 bit header. 57 * - 6 bits (PLEN, picture_header), the length (in bytes) of an extra 58 * picture header, following the VRC field. 59 * - 3 bits (PEBIT), the number of bits to ignore of the last byte 60 * of the extra picture header. (Not used at the moment.) 61 */ 62 header = AV_RB16(buf); 63 startcode = (header & 0x0400) >> 9; 64 vrc = header & 0x0200; 65 picture_header = (header & 0x01f8) >> 3; 66 buf += 2; 67 len -= 2; 68 69 if (vrc) { 70 /* Skip VRC header if present, not used at the moment. */ 71 buf += 1; 72 len -= 1; 73 } 74 if (picture_header) { 75 /* Skip extra picture header if present, not used at the moment. */ 76 buf += picture_header; 77 len -= picture_header; 78 } 79 80 if (len < 0) { 81 av_log(ctx, AV_LOG_ERROR, "Too short H.263 RTP packet\n"); 82 return AVERROR_INVALIDDATA; 83 } 84 85 if (av_new_packet(pkt, len + startcode)) { 86 av_log(ctx, AV_LOG_ERROR, "Out of memory\n"); 87 return AVERROR(ENOMEM); 88 } 89 pkt->stream_index = st->index; 90 ptr = pkt->data; 91 92 if (startcode) { 93 *ptr++ = 0; 94 *ptr++ = 0; 95 } 96 memcpy(ptr, buf, len); 97 98 return 0; 99} 100 101RTPDynamicProtocolHandler ff_h263_1998_dynamic_handler = { 102 .enc_name = "H263-1998", 103 .codec_type = AVMEDIA_TYPE_VIDEO, 104 .codec_id = AV_CODEC_ID_H263, 105 .init = h263_init, 106 .parse_packet = ff_h263_handle_packet, 107}; 108 109RTPDynamicProtocolHandler ff_h263_2000_dynamic_handler = { 110 .enc_name = "H263-2000", 111 .codec_type = AVMEDIA_TYPE_VIDEO, 112 .codec_id = AV_CODEC_ID_H263, 113 .init = h263_init, 114 .parse_packet = ff_h263_handle_packet, 115}; 116