| Line | Branch | Exec | Source |
|---|---|---|---|
| 1 | /* | ||
| 2 | * RTP parser for H.261 payload format (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 "libavcodec/get_bits.h" | ||
| 23 | #include "avformat.h" | ||
| 24 | #include "avio_internal.h" | ||
| 25 | #include "rtpdec_formats.h" | ||
| 26 | |||
| 27 | #define RTP_H261_PAYLOAD_HEADER_SIZE 4 | ||
| 28 | |||
| 29 | struct PayloadContext { | ||
| 30 | AVIOContext *buf; | ||
| 31 | uint8_t endbyte; | ||
| 32 | int endbyte_bits; | ||
| 33 | uint32_t timestamp; | ||
| 34 | }; | ||
| 35 | |||
| 36 | ✗ | static av_cold void h261_close_context(PayloadContext *pl_ctx) | |
| 37 | { | ||
| 38 | /* return if context is invalid */ | ||
| 39 | ✗ | if (!pl_ctx) | |
| 40 | ✗ | return; | |
| 41 | |||
| 42 | /* free buffer if it is valid */ | ||
| 43 | ✗ | ffio_free_dyn_buf(&pl_ctx->buf); | |
| 44 | } | ||
| 45 | |||
| 46 | ✗ | static int h261_handle_packet(AVFormatContext *ctx, PayloadContext *rtp_h261_ctx, | |
| 47 | AVStream *st, AVPacket *pkt, uint32_t *timestamp, | ||
| 48 | const uint8_t *buf, int len, uint16_t seq, | ||
| 49 | int flags) | ||
| 50 | { | ||
| 51 | int sbit, ebit, gobn, mbap, quant; | ||
| 52 | int res; | ||
| 53 | |||
| 54 | /* drop data of previous packets in case of non-continuous (lossy) packet stream */ | ||
| 55 | ✗ | if (rtp_h261_ctx->buf && rtp_h261_ctx->timestamp != *timestamp) { | |
| 56 | ✗ | ffio_free_dyn_buf(&rtp_h261_ctx->buf); | |
| 57 | ✗ | rtp_h261_ctx->endbyte_bits = 0; | |
| 58 | } | ||
| 59 | |||
| 60 | /* sanity check for size of input packet: 1 byte payload at least */ | ||
| 61 | ✗ | if (len < RTP_H261_PAYLOAD_HEADER_SIZE + 1) { | |
| 62 | ✗ | av_log(ctx, AV_LOG_ERROR, "Too short RTP/H.261 packet, got %d bytes\n", len); | |
| 63 | ✗ | return AVERROR_INVALIDDATA; | |
| 64 | } | ||
| 65 | |||
| 66 | /* | ||
| 67 | * decode the H.261 payload header according to section 4.1 of RFC 4587: | ||
| 68 | * (uses 4 bytes between RTP header and H.261 stream per packet) | ||
| 69 | * | ||
| 70 | * 0 1 2 3 | ||
| 71 | * 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 | ||
| 72 | * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ||
| 73 | * |SBIT |EBIT |I|V| GOBN | MBAP | QUANT | HMVD | VMVD | | ||
| 74 | * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ||
| 75 | * | ||
| 76 | * Start bit position (SBIT): 3 bits | ||
| 77 | * End bit position (EBIT): 3 bits | ||
| 78 | * INTRA-frame encoded data (I): 1 bit | ||
| 79 | * Motion Vector flag (V): 1 bit | ||
| 80 | * GOB number (GOBN): 4 bits | ||
| 81 | * Macroblock address predictor (MBAP): 5 bits | ||
| 82 | * Quantizer (QUANT): 5 bits | ||
| 83 | * Horizontal motion vector data (HMVD): 5 bits | ||
| 84 | * Vertical motion vector data (VMVD): 5 bits | ||
| 85 | */ | ||
| 86 | ✗ | sbit = (buf[0] >> 5) & 0x07; | |
| 87 | ✗ | ebit = (buf[0] >> 2) & 0x07; | |
| 88 | ✗ | gobn = (buf[1] >> 4) & 0x0f; | |
| 89 | ✗ | mbap = ((buf[1] << 1) & 0x1e) | ((buf[2] >> 7) & 0x01); | |
| 90 | ✗ | quant = (buf[2] >> 2) & 0x1f; | |
| 91 | |||
| 92 | /* pass the H.261 payload header and continue with the actual payload */ | ||
| 93 | ✗ | buf += RTP_H261_PAYLOAD_HEADER_SIZE; | |
| 94 | ✗ | len -= RTP_H261_PAYLOAD_HEADER_SIZE; | |
| 95 | |||
| 96 | /* start frame buffering with new dynamic buffer */ | ||
| 97 | ✗ | if (!rtp_h261_ctx->buf) { | |
| 98 | /* sanity check: a new frame starts with gobn=0, sbit=0, mbap=0, quant=0 */ | ||
| 99 | ✗ | if (!gobn && !sbit && !mbap && !quant) { | |
| 100 | ✗ | res = avio_open_dyn_buf(&rtp_h261_ctx->buf); | |
| 101 | ✗ | if (res < 0) | |
| 102 | ✗ | return res; | |
| 103 | /* update the timestamp in the frame packet with the one from the RTP packet */ | ||
| 104 | ✗ | rtp_h261_ctx->timestamp = *timestamp; | |
| 105 | } else { | ||
| 106 | /* frame not started yet, need more packets */ | ||
| 107 | ✗ | return AVERROR(EAGAIN); | |
| 108 | } | ||
| 109 | } | ||
| 110 | |||
| 111 | /* do the "byte merging" at the boundaries of two consecutive frame fragments */ | ||
| 112 | ✗ | if (rtp_h261_ctx->endbyte_bits || sbit) { | |
| 113 | ✗ | if (rtp_h261_ctx->endbyte_bits == sbit) { | |
| 114 | ✗ | rtp_h261_ctx->endbyte |= buf[0] & (0xff >> sbit); | |
| 115 | ✗ | rtp_h261_ctx->endbyte_bits = 0; | |
| 116 | ✗ | buf++; | |
| 117 | ✗ | len--; | |
| 118 | ✗ | avio_w8(rtp_h261_ctx->buf, rtp_h261_ctx->endbyte); | |
| 119 | } else { | ||
| 120 | /* ebit/sbit values inconsistent, assuming packet loss */ | ||
| 121 | GetBitContext gb; | ||
| 122 | ✗ | res = init_get_bits(&gb, buf, len*8 - ebit); | |
| 123 | ✗ | if (res < 0) | |
| 124 | ✗ | return res; | |
| 125 | ✗ | skip_bits(&gb, sbit); | |
| 126 | ✗ | if (rtp_h261_ctx->endbyte_bits) { | |
| 127 | ✗ | rtp_h261_ctx->endbyte |= get_bits(&gb, 8 - rtp_h261_ctx->endbyte_bits); | |
| 128 | ✗ | avio_w8(rtp_h261_ctx->buf, rtp_h261_ctx->endbyte); | |
| 129 | } | ||
| 130 | ✗ | while (get_bits_left(&gb) >= 8) | |
| 131 | ✗ | avio_w8(rtp_h261_ctx->buf, get_bits(&gb, 8)); | |
| 132 | ✗ | rtp_h261_ctx->endbyte_bits = get_bits_left(&gb); | |
| 133 | ✗ | if (rtp_h261_ctx->endbyte_bits) | |
| 134 | ✗ | rtp_h261_ctx->endbyte = get_bits(&gb, rtp_h261_ctx->endbyte_bits) << | |
| 135 | ✗ | (8 - rtp_h261_ctx->endbyte_bits); | |
| 136 | ✗ | ebit = 0; | |
| 137 | ✗ | len = 0; | |
| 138 | } | ||
| 139 | } | ||
| 140 | ✗ | if (ebit) { | |
| 141 | ✗ | if (len > 0) | |
| 142 | ✗ | avio_write(rtp_h261_ctx->buf, buf, len - 1); | |
| 143 | ✗ | rtp_h261_ctx->endbyte_bits = 8 - ebit; | |
| 144 | ✗ | rtp_h261_ctx->endbyte = buf[len - 1] & (0xff << ebit); | |
| 145 | } else { | ||
| 146 | ✗ | avio_write(rtp_h261_ctx->buf, buf, len); | |
| 147 | } | ||
| 148 | |||
| 149 | /* RTP marker bit means: last fragment of current frame was received; | ||
| 150 | otherwise, an additional fragment is needed for the current frame */ | ||
| 151 | ✗ | if (!(flags & RTP_FLAG_MARKER)) | |
| 152 | ✗ | return AVERROR(EAGAIN); | |
| 153 | |||
| 154 | /* write the completed last byte from the "byte merging" */ | ||
| 155 | ✗ | if (rtp_h261_ctx->endbyte_bits) | |
| 156 | ✗ | avio_w8(rtp_h261_ctx->buf, rtp_h261_ctx->endbyte); | |
| 157 | ✗ | rtp_h261_ctx->endbyte_bits = 0; | |
| 158 | |||
| 159 | /* close frame buffering and create resulting A/V packet */ | ||
| 160 | ✗ | res = ff_rtp_finalize_packet(pkt, &rtp_h261_ctx->buf, st->index); | |
| 161 | ✗ | if (res < 0) | |
| 162 | ✗ | return res; | |
| 163 | |||
| 164 | ✗ | return 0; | |
| 165 | } | ||
| 166 | |||
| 167 | const RTPDynamicProtocolHandler ff_h261_dynamic_handler = { | ||
| 168 | .enc_name = "H261", | ||
| 169 | .codec_type = AVMEDIA_TYPE_VIDEO, | ||
| 170 | .codec_id = AV_CODEC_ID_H261, | ||
| 171 | .need_parsing = AVSTREAM_PARSE_FULL, | ||
| 172 | .priv_data_size = sizeof(PayloadContext), | ||
| 173 | .close = h261_close_context, | ||
| 174 | .parse_packet = h261_handle_packet, | ||
| 175 | .static_payload_id = 31, | ||
| 176 | }; | ||
| 177 |