Libav
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00001 /* 00002 * RTP H.263 Depacketizer, RFC 4629 00003 * Copyright (c) 2010 Martin Storsjo 00004 * 00005 * This file is part of FFmpeg. 00006 * 00007 * FFmpeg is free software; you can redistribute it and/or 00008 * modify it under the terms of the GNU Lesser General Public 00009 * License as published by the Free Software Foundation; either 00010 * version 2.1 of the License, or (at your option) any later version. 00011 * 00012 * FFmpeg is distributed in the hope that it will be useful, 00013 * but WITHOUT ANY WARRANTY; without even the implied warranty of 00014 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 00015 * Lesser General Public License for more details. 00016 * 00017 * You should have received a copy of the GNU Lesser General Public 00018 * License along with FFmpeg; if not, write to the Free Software 00019 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 00020 */ 00021 00022 #include "avformat.h" 00023 #include "rtpdec_h263.h" 00024 #include "libavutil/intreadwrite.h" 00025 00026 static int h263_handle_packet(AVFormatContext *ctx, 00027 PayloadContext *data, 00028 AVStream *st, 00029 AVPacket * pkt, 00030 uint32_t * timestamp, 00031 const uint8_t * buf, 00032 int len, int flags) 00033 { 00034 uint8_t *ptr; 00035 uint16_t header; 00036 int startcode, vrc, picture_header; 00037 00038 if (len < 2) { 00039 av_log(ctx, AV_LOG_ERROR, "Too short H.263 RTP packet\n"); 00040 return AVERROR_INVALIDDATA; 00041 } 00042 00043 /* Decode the 16 bit H.263+ payload header, as described in section 00044 * 5.1 of RFC 4629. The fields of this header are: 00045 * - 5 reserved bits, should be ignored. 00046 * - One bit (P, startcode), indicating a picture start, picture segment 00047 * start or video sequence end. If set, two zero bytes should be 00048 * prepended to the payload. 00049 * - One bit (V, vrc), indicating the presence of an 8 bit Video 00050 * Redundancy Coding field after this 16 bit header. 00051 * - 6 bits (PLEN, picture_header), the length (in bytes) of an extra 00052 * picture header, following the VRC field. 00053 * - 3 bits (PEBIT), the number of bits to ignore of the last byte 00054 * of the extra picture header. (Not used at the moment.) 00055 */ 00056 header = AV_RB16(buf); 00057 startcode = (header & 0x0400) >> 9; 00058 vrc = header & 0x0200; 00059 picture_header = (header & 0x01f8) >> 3; 00060 buf += 2; 00061 len -= 2; 00062 00063 if (vrc) { 00064 /* Skip VRC header if present, not used at the moment. */ 00065 buf += 1; 00066 len -= 1; 00067 } 00068 if (picture_header) { 00069 /* Skip extra picture header if present, not used at the moment. */ 00070 buf += picture_header; 00071 len -= picture_header; 00072 } 00073 00074 if (len < 0) { 00075 av_log(ctx, AV_LOG_ERROR, "Too short H.263 RTP packet\n"); 00076 return AVERROR_INVALIDDATA; 00077 } 00078 00079 if (av_new_packet(pkt, len + startcode)) { 00080 av_log(ctx, AV_LOG_ERROR, "Out of memory\n"); 00081 return AVERROR(ENOMEM); 00082 } 00083 pkt->stream_index = st->index; 00084 ptr = pkt->data; 00085 00086 if (startcode) { 00087 *ptr++ = 0; 00088 *ptr++ = 0; 00089 } 00090 memcpy(ptr, buf, len); 00091 00092 return 0; 00093 } 00094 00095 RTPDynamicProtocolHandler ff_h263_1998_dynamic_handler = { 00096 .enc_name = "H263-1998", 00097 .codec_type = AVMEDIA_TYPE_VIDEO, 00098 .codec_id = CODEC_ID_H263, 00099 .parse_packet = h263_handle_packet, 00100 }; 00101 00102 RTPDynamicProtocolHandler ff_h263_2000_dynamic_handler = { 00103 .enc_name = "H263-2000", 00104 .codec_type = AVMEDIA_TYPE_VIDEO, 00105 .codec_id = CODEC_ID_H263, 00106 .parse_packet = h263_handle_packet, 00107 }; 00108