diff options
Diffstat (limited to 'libavformat/rtpdec_h261.c')
-rw-r--r-- | libavformat/rtpdec_h261.c | 205 |
1 files changed, 205 insertions, 0 deletions
diff --git a/libavformat/rtpdec_h261.c b/libavformat/rtpdec_h261.c new file mode 100644 index 0000000000..b902d2aa40 --- /dev/null +++ b/libavformat/rtpdec_h261.c @@ -0,0 +1,205 @@ +/* + * RTP parser for H.261 payload format (RFC 4587) + * Copyright (c) 2014 Thomas Volkert <thomas@homer-conferencing.com> + * + * This file is part of FFmpeg. + * + * FFmpeg is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * FFmpeg is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with FFmpeg; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + */ + +#include "avformat.h" +#include "rtpdec_formats.h" +#include "libavcodec/get_bits.h" + +#define RTP_H261_PAYLOAD_HEADER_SIZE 4 + +struct PayloadContext { + AVIOContext *buf; + uint8_t endbyte; + int endbyte_bits; + uint32_t timestamp; +}; + +static PayloadContext *h261_new_context(void) +{ + return av_mallocz(sizeof(PayloadContext)); +} + +static void h261_free_dyn_buffer(AVIOContext **dyn_buf) +{ + uint8_t *ptr_dyn_buffer; + avio_close_dyn_buf(*dyn_buf, &ptr_dyn_buffer); + av_free(ptr_dyn_buffer); + *dyn_buf = NULL; +} + +static void h261_free_context(PayloadContext *pl_ctx) +{ + /* return if context is invalid */ + if (!pl_ctx) + return; + + /* free buffer if it is valid */ + if (pl_ctx->buf) { + h261_free_dyn_buffer(&pl_ctx->buf); + } + + /* free context */ + av_free(pl_ctx); +} + +static av_cold int h261_init(AVFormatContext *ctx, int st_index, + PayloadContext *data) +{ + //av_log(ctx, AV_LOG_DEBUG, "h261_init() for stream %d\n", st_index); + + if (st_index < 0) + return 0; + + ctx->streams[st_index]->need_parsing = AVSTREAM_PARSE_FULL; + + return 0; +} + +int ff_h261_handle_packet(AVFormatContext *ctx, PayloadContext *data, + AVStream *st, AVPacket *pkt, uint32_t *timestamp, + const uint8_t *buf, int len, uint16_t seq, int flags) +{ + int sbit, ebit, gobn, mbap, quant; + int res; + + //av_log(ctx, AV_LOG_DEBUG, "got h261 RTP packet with time: %u\n", timestamp); + + /* drop data of previous packets in case of non-continuous (loss) packet stream */ + if (data->buf && data->timestamp != *timestamp) { + h261_free_dyn_buffer(&data->buf); + } + + /* sanity check for size of input packet */ + if (len < 5 /* 4 bytes header and 1 byte payload at least */) { + av_log(ctx, AV_LOG_ERROR, "Too short H.261 RTP packet\n"); + return AVERROR_INVALIDDATA; + } + + /* + decode the H.261 payload header according to section 4.1 of RFC 4587: + (uses 4 bytes between RTP header and H.261 stream per packet) + + 0 1 2 3 + 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 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + |SBIT |EBIT |I|V| GOBN | MBAP | QUANT | HMVD | VMVD | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + Start bit position (SBIT): 3 bits + End bit position (EBIT): 3 bits + INTRA-frame encoded data (I): 1 bit + Motion Vector flag (V): 1 bit + GOB number (GOBN): 4 bits + Macroblock address predictor (MBAP): 5 bits + Quantizer (QUANT): 5 bits + Horizontal motion vector data (HMVD): 5 bits + Vertical motion vector data (VMVD): 5 bits + + */ + sbit = (buf[0] >> 5) & 0x07; + ebit = (buf[0] >> 2) & 0x07; + gobn = (buf[1] >> 4) & 0x0f; + mbap = ((buf[1] << 1) & 0x1e) | ((buf[2] >> 7) & 0x01); + quant = (buf[2] >> 2) & 0x1f; + + /* pass the H.261 payload header and continue with the actual payload */ + buf += RTP_H261_PAYLOAD_HEADER_SIZE; + len -= RTP_H261_PAYLOAD_HEADER_SIZE; + + /* start frame buffering with new dynamic buffer */ + if (!data->buf) { + /* sanity check: a new frame starts with gobn=0, sbit=0, mbap=0, uqnat=0 */ + if (!gobn && !sbit && !mbap && !quant){ + res = avio_open_dyn_buf(&data->buf); + if (res < 0) + return res; + /* update the timestamp in the frame packet with the one from the RTP packet */ + data->timestamp = *timestamp; + } else { + /* frame not started yet, need more packets */ + return AVERROR(EAGAIN); + } + } + + /* do the "byte merging" at the boundaries of two consecutive frame fragments */ + if (data->endbyte_bits || sbit) { + if (data->endbyte_bits == sbit) { + data->endbyte |= buf[0] & (0xff >> sbit); + data->endbyte_bits = 0; + buf++; + len--; + avio_w8(data->buf, data->endbyte); + } else { + /* ebit/sbit values inconsistent, assuming packet loss */ + GetBitContext gb; + init_get_bits(&gb, buf, len*8 - ebit); + skip_bits(&gb, sbit); + if (data->endbyte_bits) { + data->endbyte |= get_bits(&gb, 8 - data->endbyte_bits); + avio_w8(data->buf, data->endbyte); + } + while (get_bits_left(&gb) >= 8) + avio_w8(data->buf, get_bits(&gb, 8)); + data->endbyte_bits = get_bits_left(&gb); + if (data->endbyte_bits) + data->endbyte = get_bits(&gb, data->endbyte_bits) << + (8 - data->endbyte_bits); + ebit = 0; + len = 0; + } + } + if (ebit) { + if (len > 0) + avio_write(data->buf, buf, len - 1); + data->endbyte_bits = 8 - ebit; + data->endbyte = buf[len - 1] & (0xff << ebit); + } else { + avio_write(data->buf, buf, len); + } + + /* RTP marker bit means: last fragment of current frame was received; + otherwise, an additional fragment is needed for the current frame */ + if (!(flags & RTP_FLAG_MARKER)) + return AVERROR(EAGAIN); + + /* write the completed last byte from the "byte merging" */ + if (data->endbyte_bits) + avio_w8(data->buf, data->endbyte); + data->endbyte_bits = 0; + + /* close frame buffering and create resulting A/V packet */ + res = ff_rtp_finalize_packet(pkt, &data->buf, st->index); + if (res < 0) + return res; + + return 0; +} + +RTPDynamicProtocolHandler ff_h261_dynamic_handler = { + .enc_name = "H261", + .codec_type = AVMEDIA_TYPE_VIDEO, + .codec_id = AV_CODEC_ID_H261, + .init = h261_init, + .parse_packet = ff_h261_handle_packet, + .alloc = h261_new_context, + .free = h261_free_context, + .static_payload_id = 31, +}; |