ffm.c

ffmpeg源码分析

/*
 * FFM (ffserver live feed) encoder and decoder
 * Copyright (c) 2001 Fabrice Bellard.
 *
 * This library 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 of the License, or (at your option) any later version.
 *
 * This library 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 this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */
#include "avformat.h"
#include <unistd.h>

/* The FFM file is made of blocks of fixed size */
#define FFM_HEADER_SIZE 14
#define PACKET_ID       0x666d

/* each packet contains frames (which can span several packets */
#define FRAME_HEADER_SIZE    8
#define FLAG_KEY_FRAME       0x01

typedef struct FFMStream {
    int64_t pts;
} FFMStream;

enum {
    READ_HEADER,
    READ_DATA,
};

typedef struct FFMContext {
    /* only reading mode */
    offset_t write_index, file_size;
    int read_state;
    uint8_t header[FRAME_HEADER_SIZE];

    /* read and write */
    int first_packet; /* true if first packet, needed to set the discontinuity tag */
    int first_frame_in_packet; /* true if first frame in packet, needed to know if PTS information is valid */
    int packet_size;
    int frame_offset;
    int64_t pts;
    uint8_t *packet_ptr, *packet_end;
    uint8_t packet[FFM_PACKET_SIZE];
} FFMContext;

static int64_t get_pts(AVFormatContext *s, offset_t pos);

/* disable pts hack for testing */
int ffm_nopts = 0;

#ifdef CONFIG_MUXERS
static void flush_packet(AVFormatContext *s)
{
    FFMContext *ffm = s->priv_data;
    int fill_size, h;
    ByteIOContext *pb = &s->pb;

    fill_size = ffm->packet_end - ffm->packet_ptr;
    memset(ffm->packet_ptr, 0, fill_size);

    if (url_ftell(pb) % ffm->packet_size)
        av_abort();

    /* put header */
    put_be16(pb, PACKET_ID);
    put_be16(pb, fill_size);
    put_be64(pb, ffm->pts);
    h = ffm->frame_offset;
    if (ffm->first_packet)
        h |= 0x8000;
    put_be16(pb, h);
    put_buffer(pb, ffm->packet, ffm->packet_end - ffm->packet);
    put_flush_packet(pb);

    /* prepare next packet */
    ffm->frame_offset = 0; /* no key frame */
    ffm->pts = 0; /* no pts */
    ffm->packet_ptr = ffm->packet;
    ffm->first_packet = 0;
}

/* 'first' is true if first data of a frame */
static void ffm_write_data(AVFormatContext *s,
                           const uint8_t *buf, int size,
                           int64_t pts, int first)
{
    FFMContext *ffm = s->priv_data;
    int len;

    if (first && ffm->frame_offset == 0)
        ffm->frame_offset = ffm->packet_ptr - ffm->packet + FFM_HEADER_SIZE;
    if (first && ffm->pts == 0)
        ffm->pts = pts;

    /* write as many packets as needed */
    while (size > 0) {
        len = ffm->packet_end - ffm->packet_ptr;
        if (len > size)
            len = size;
        memcpy(ffm->packet_ptr, buf, len);

        ffm->packet_ptr += len;
        buf += len;
        size -= len;
        if (ffm->packet_ptr >= ffm->packet_end) {
            /* special case : no pts in packet : we leave the current one */
            if (ffm->pts == 0)
                ffm->pts = pts;

            flush_packet(s);
        }
    }
}

static int ffm_write_header(AVFormatContext *s)
{
    FFMContext *ffm = s->priv_data;
    AVStream *st;
    FFMStream *fst;
    ByteIOContext *pb = &s->pb;
    AVCodecContext *codec;
    int bit_rate, i;

    ffm->packet_size = FFM_PACKET_SIZE;

    /* header */
    put_le32(pb, MKTAG('F', 'F', 'M', '1'));
    put_be32(pb, ffm->packet_size);
    /* XXX: store write position in other file ? */
    put_be64(pb, ffm->packet_size); /* current write position */

    put_be32(pb, s->nb_streams);
    bit_rate = 0;
    for(i=0;i<s->nb_streams;i++) {
        st = s->streams[i];
        bit_rate += st->codec->bit_rate;
    }
    put_be32(pb, bit_rate);

    /* list of streams */
    for(i=0;i<s->nb_streams;i++) {
        st = s->streams[i];
        fst = av_mallocz(sizeof(FFMStream));
        if (!fst)
            goto fail;
        av_set_pts_info(st, 64, 1, 1000000);
        st->priv_data = fst;

        codec = st->codec;
        /* generic info */
        put_be32(pb, codec->codec_id);
        put_byte(pb, codec->codec_type);
        put_be32(pb, codec->bit_rate);
        put_be32(pb, st->quality);
        put_be32(pb, codec->flags);
        put_be32(pb, codec->flags2);
        put_be32(pb, codec->debug);
        /* specific info */
        switch(codec->codec_type) {
        case CODEC_TYPE_VIDEO:
            put_be32(pb, codec->time_base.num);
            put_be32(pb, codec->time_base.den);
            put_be16(pb, codec->width);
            put_be16(pb, codec->height);
            put_be16(pb, codec->gop_size);
            put_be32(pb, codec->pix_fmt);
            put_byte(pb, codec->qmin);
            put_byte(pb, codec->qmax);
            put_byte(pb, codec->max_qdiff);
            put_be16(pb, (int) (codec->qcompress * 10000.0));
            put_be16(pb, (int) (codec->qblur * 10000.0));
            put_be32(pb, codec->bit_rate_tolerance);
            put_strz(pb, codec->rc_eq);
            put_be32(pb, codec->rc_max_rate);
            put_be32(pb, codec->rc_min_rate);
            put_be32(pb, codec->rc_buffer_size);
            put_be64(pb, av_dbl2int(codec->i_quant_factor));
            put_be64(pb, av_dbl2int(codec->b_quant_factor));
            put_be64(pb, av_dbl2int(codec->i_quant_offset));
            put_be64(pb, av_dbl2int(codec->b_quant_offset));
            put_be32(pb, codec->dct_algo);
            put_be32(pb, codec->strict_std_compliance);
            put_be32(pb, codec->max_b_frames);
            put_be32(pb, codec->luma_elim_threshold);
            put_be32(pb, codec->chroma_elim_threshold);
            put_be32(pb, codec->mpeg_quant);
            put_be32(pb, codec->intra_dc_precision);
            put_be32(pb, codec->me_method);
            put_be32(pb, codec->mb_decision);
            put_be32(pb, codec->nsse_weight);
            put_be32(pb, codec->frame_skip_cmp);
            put_be64(pb, av_dbl2int(codec->rc_buffer_aggressivity));
            break;
        case CODEC_TYPE_AUDIO:
            put_be32(pb, codec->sample_rate);
            put_le16(pb, codec->channels);
            put_le16(pb, codec->frame_size);
            break;
        default:
            return -1;
        }
        /* hack to have real time */
        if (ffm_nopts)
            fst->pts = 0;
        else
            fst->pts = av_gettime();
    }

    /* flush until end of block reached */
    while ((url_ftell(pb) % ffm->packet_size) != 0)
        put_byte(pb, 0);

    put_flush_packet(pb);

    /* init packet mux */
    ffm->packet_ptr = ffm->packet;
    ffm->packet_end = ffm->packet + ffm->packet_size - FFM_HEADER_SIZE;
    assert(ffm->packet_end >= ffm->packet);
    ffm->frame_offset = 0;
    ffm->pts = 0;
    ffm->first_packet = 1;

    return 0;
 fail:
    for(i=0;i<s->nb_streams;i++) {
        st = s->streams[i];
        av_freep(&st->priv_data);
    }
    return -1;
}

static int ffm_write_packet(AVFormatContext *s, AVPacket *pkt)
{
    AVStream *st = s->streams[pkt->stream_index];
    FFMStream *fst = st->priv_data;
    int64_t pts;
    uint8_t header[FRAME_HEADER_SIZE];
    int duration;
    int size= pkt->size;

    //XXX/FIXME use duration from pkt
    if (st->codec->codec_type == CODEC_TYPE_AUDIO) {
        duration = ((float)st->codec->frame_size / st->codec->sample_rate * 1000000.0);
    } else {
        duration = (1000000.0 * st->codec->time_base.num / (float)st->codec->time_base.den);
    }

    pts = fst->pts;
    /* packet size & key_frame */
    header[0] = pkt->stream_index;
    header[1] = 0;
    if (pkt->flags & PKT_FLAG_KEY)
        header[1] |= FLAG_KEY_FRAME;
    header[2] = (size >> 16) & 0xff;
    header[3] = (size >> 8) & 0xff;
    header[4] = size & 0xff;
    header[5] = (duration >> 16) & 0xff;
    header[6] = (duration >> 8) & 0xff;
    header[7] = duration & 0xff;
    ffm_write_data(s, header, FRAME_HEADER_SIZE, pts, 1);
    ffm_write_data(s, pkt->data, size, pts, 0);

    fst->pts += duration;
    return 0;
}

static int ffm_write_trailer(AVFormatContext *s)
{
    ByteIOContext *pb = &s->pb;
    FFMContext *ffm = s->priv_data;

    /* flush packets */
    if (ffm->packet_ptr > ffm->packet)
        flush_packet(s);

    put_flush_packet(pb);

    if (!url_is_streamed(pb)) {
        int64_t size;
        /* update the write offset */
        size = url_ftell(pb);
        url_fseek(pb, 8, SEEK_SET);
        put_be64(pb, size);
        put_flush_packet(pb);
    }

    return 0;
}
#endif //CONFIG_MUXERS

/* ffm demux */

static int ffm_is_avail_data(AVFormatContext *s, int size)
{
    FFMContext *ffm = s->priv_data;
    offset_t pos, avail_size;
    int len;

    len = ffm->packet_end - ffm->packet_ptr;
    if (!ffm_nopts) {
        /* XXX: I don't understand this test, so I disabled it for testing */
        if (size <= len)
            return 1;
    }
    pos = url_ftell(&s->pb);
    if (pos == ffm->write_index) {
        /* exactly at the end of stream */
        return 0;
    } else if (pos < ffm->write_index) {
        avail_size = ffm->write_index - pos;
    } else {
        avail_size = (ffm->file_size - pos) + (ffm->write_index - FFM_PACKET_SIZE);
    }
    avail_size = (avail_size / ffm->packet_size) * (ffm->packet_size - FFM_HEADER_SIZE) + len;
    if (size <= avail_size)
        return 1;
    else
        return 0;
}

/* first is true if we read the frame header */
static int ffm_read_data(AVFormatContext *s,
                         uint8_t *buf, int size, int first)
{
    FFMContext *ffm = s->priv_data;
    ByteIOContext *pb = &s->pb;
    int len, fill_size, size1, frame_offset;

    size1 = size;
    while (size > 0) {
    redo:
        len = ffm->packet_end - ffm->packet_ptr;
        if (len > size)
            len = size;
        if (len == 0) {
            if (url_ftell(pb) == ffm->file_size)
                url_fseek(pb, ffm->packet_size, SEEK_SET);
    retry_read:
            get_be16(pb); /* PACKET_ID */
            fill_size = get_be16(pb);
            ffm->pts = get_be64(pb);
            ffm->first_frame_in_packet = 1;
            frame_offset = get_be16(pb);
            get_buffer(pb, ffm->packet, ffm->packet_size - FFM_HEADER_SIZE);
            ffm->packet_end = ffm->packet + (ffm->packet_size - FFM_HEADER_SIZE - fill_size);
            if (ffm->packet_end < ffm->packet)
                return -1;
            /* if first packet or resynchronization packet, we must
               handle it specifically */
            if (ffm->first_packet || (frame_offset & 0x8000)) {
                if (!frame_offset) {
                    /* This packet has no frame headers in it */
                    if (url_ftell(pb) >= ffm->packet_size * 3) {
                        url_fseek(pb, -ffm->packet_size * 2, SEEK_CUR);
                        goto retry_read;
                    }
                    /* This is bad, we cannot find a valid frame header */
                    return 0;
                }
                ffm->first_packet = 0;
                if ((frame_offset & 0x7ffff) < FFM_HEADER_SIZE)
                    return -1;
                ffm->packet_ptr = ffm->packet + (frame_offset & 0x7fff) - FFM_HEADER_SIZE;
                if (!first)
                    break;
            } else {
                ffm->packet_ptr = ffm->packet;
            }
            goto redo;
        }
        memcpy(buf, ffm->packet_ptr, len);
        buf += len;
        ffm->packet_ptr += len;
        size -= len;
        first = 0;
    }
    return size1 - size;
}


static void adjust_write_index(AVFormatContext *s)
{
    FFMContext *ffm = s->priv_data;
    ByteIOContext *pb = &s->pb;
    int64_t pts;
    //offset_t orig_write_index = ffm->write_index;
    offset_t pos_min, pos_max;
    int64_t pts_start;
    offset_t ptr = url_ftell(pb);