PeerStreamer

/*

 * RTP AMR Depacketizer, RFC 3267

 * Copyright (c) 2010 Martin Storsjo

 *

 * 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_amr.h"

#include "libavutil/avstring.h"

static const uint8_t frame_sizes_nb[16] = {

    12, 13, 15, 17, 19, 20, 26, 31, 5, 0, 0, 0, 0, 0, 0, 0

};

static const uint8_t frame_sizes_wb[16] = {

    17, 23, 32, 36, 40, 46, 50, 58, 60, 5, 5, 0, 0, 0, 0, 0

};

static int amr_handle_packet(AVFormatContext *ctx,

                             PayloadContext *data,

                             AVStream *st,

                             AVPacket * pkt,

                             uint32_t * timestamp,

                             const uint8_t * buf,

                             int len, int flags)

{

    const uint8_t *frame_sizes = NULL;

    int frames;

    int i;

    const uint8_t *speech_data;

    uint8_t *ptr;

    if (st->codec->codec_id == CODEC_ID_AMR_NB) {

        frame_sizes = frame_sizes_nb;

    } else if (st->codec->codec_id == CODEC_ID_AMR_WB) {

        frame_sizes = frame_sizes_wb;

    } else {

        av_log(ctx, AV_LOG_ERROR, "Bad codec ID\n");

        return AVERROR_INVALIDDATA;

    }

    if (st->codec->channels != 1) {

        av_log(ctx, AV_LOG_ERROR, "Only mono AMR is supported\n");

        return AVERROR_INVALIDDATA;

    }

    /* The AMR RTP packet consists of one header byte, followed

     * by one TOC byte for each AMR frame in the packet, followed

     * by the speech data for all the AMR frames.

     *

     * The header byte contains only a codec mode request, for

     * requesting what kind of AMR data the sender wants to

     * receive. Not used at the moment.

     */

    /* Count the number of frames in the packet. The highest bit

     * is set in a TOC byte if there are more frames following.

     */

    for (frames = 1; frames < len && (buf[frames] & 0x80); frames++) ;

    if (1 + frames >= len) {

        /* We hit the end of the packet while counting frames. */

        av_log(ctx, AV_LOG_ERROR, "No speech data found\n");

        return AVERROR_INVALIDDATA;

    }

    speech_data = buf + 1 + frames;

    /* Everything except the codec mode request byte should be output. */

    if (av_new_packet(pkt, len - 1)) {

        av_log(ctx, AV_LOG_ERROR, "Out of memory\n");

        return AVERROR(ENOMEM);

    }

    pkt->stream_index = st->index;

    ptr = pkt->data;

    for (i = 0; i < frames; i++) {

        uint8_t toc = buf[1 + i];

        int frame_size = frame_sizes[(toc >> 3) & 0x0f];

        if (speech_data + frame_size > buf + len) {

            /* Too little speech data */

            av_log(ctx, AV_LOG_WARNING, "Too little speech data in the RTP packet\n");

            /* Set the unwritten part of the packet to zero. */

            memset(ptr, 0, pkt->data + pkt->size - ptr);

            pkt->size = ptr - pkt->data;

            return 0;

        }

        /* Extract the AMR frame mode from the TOC byte */

        *ptr++ = toc & 0x7C;

        /* Copy the speech data */

        memcpy(ptr, speech_data, frame_size);

        speech_data += frame_size;

        ptr += frame_size;

    }

    if (speech_data < buf + len) {

        av_log(ctx, AV_LOG_WARNING, "Too much speech data in the RTP packet?\n");

        /* Set the unwritten part of the packet to zero. */

        memset(ptr, 0, pkt->data + pkt->size - ptr);

        pkt->size = ptr - pkt->data;

    }

    return 0;

}

static int amr_parse_sdp_line(AVFormatContext *s, int st_index,

                              PayloadContext *data, const char *line)

{

    const char *p;

    char attr[25], value[25];

    /* Parse an fmtp line this one:

     * a=fmtp:97 octet-align=1; interleaving=0

     * That is, a normal fmtp: line followed by semicolon & space

     * separated key/value pairs.

     */

    if (av_strstart(line, "fmtp:", &p)) {

        int octet_align = 0;

        int crc = 0;

        int interleaving = 0;

        int channels = 1;

        while (*p && *p == ' ') p++; /* strip spaces */

        while (*p && *p != ' ') p++; /* eat protocol identifier */

        while (*p && *p == ' ') p++; /* strip trailing spaces */

        while (ff_rtsp_next_attr_and_value(&p, attr, sizeof(attr), value, sizeof(value))) {

            /* Some AMR SDP configurations contain "octet-align", without

             * the trailing =1. Therefore, if the value is empty,

             * interpret it as "1".

             */

            if (!strcmp(value, "")) {

                av_log(s, AV_LOG_WARNING, "AMR fmtp attribute %s had "

                                          "nonstandard empty value\n", attr);

                strcpy(value, "1");

            }

            if (!strcmp(attr, "octet-align"))

                octet_align = atoi(value);

            else if (!strcmp(attr, "crc"))

                crc = atoi(value);

            else if (!strcmp(attr, "interleaving"))

                interleaving = atoi(value);

            else if (!strcmp(attr, "channels"))

                channels = atoi(value);

        }

        if (!octet_align || crc || interleaving || channels != 1) {

            av_log(s, AV_LOG_ERROR, "Unsupported RTP/AMR configuration!\n");

            return -1;

        }

    }

    return 0;

}

RTPDynamicProtocolHandler ff_amr_nb_dynamic_handler = {

    .enc_name         = "AMR",

    .codec_type       = AVMEDIA_TYPE_AUDIO,

    .codec_id         = CODEC_ID_AMR_NB,

    .parse_sdp_a_line = amr_parse_sdp_line,

    .parse_packet     = amr_handle_packet,

};

RTPDynamicProtocolHandler ff_amr_wb_dynamic_handler = {

    .enc_name         = "AMR-WB",

    .codec_type       = AVMEDIA_TYPE_AUDIO,

    .codec_id         = CODEC_ID_AMR_WB,

    .parse_sdp_a_line = amr_parse_sdp_line,

    .parse_packet     = amr_handle_packet,

};