asf.c

ffmpeg源码分析

/*
 * ASF compatible decoder.
 * Copyright (c) 2000, 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 "avi.h"
#include "mpegaudio.h"
#include "asf.h"

#undef NDEBUG
#include <assert.h>

#define FRAME_HEADER_SIZE 17
// Fix Me! FRAME_HEADER_SIZE may be different.

static const GUID index_guid = {
    0x33000890, 0xe5b1, 0x11cf, { 0x89, 0xf4, 0x00, 0xa0, 0xc9, 0x03, 0x49, 0xcb },
};

/**********************************/
/* decoding */

//#define DEBUG

#ifdef DEBUG
#define PRINT_IF_GUID(g,cmp) \
if (!memcmp(g, &cmp, sizeof(GUID))) \
    printf("(GUID: %s) ", #cmp)

static void print_guid(const GUID *g)
{
    int i;
    PRINT_IF_GUID(g, asf_header);
    else PRINT_IF_GUID(g, file_header);
    else PRINT_IF_GUID(g, stream_header);
    else PRINT_IF_GUID(g, audio_stream);
    else PRINT_IF_GUID(g, audio_conceal_none);
    else PRINT_IF_GUID(g, video_stream);
    else PRINT_IF_GUID(g, video_conceal_none);
    else PRINT_IF_GUID(g, command_stream);
    else PRINT_IF_GUID(g, comment_header);
    else PRINT_IF_GUID(g, codec_comment_header);
    else PRINT_IF_GUID(g, codec_comment1_header);
    else PRINT_IF_GUID(g, data_header);
    else PRINT_IF_GUID(g, index_guid);
    else PRINT_IF_GUID(g, head1_guid);
    else PRINT_IF_GUID(g, head2_guid);
    else PRINT_IF_GUID(g, my_guid);
    else PRINT_IF_GUID(g, ext_stream_header);
    else PRINT_IF_GUID(g, extended_content_header);
    else PRINT_IF_GUID(g, ext_stream_embed_stream_header);
    else PRINT_IF_GUID(g, ext_stream_audio_stream);
    else
        printf("(GUID: unknown) ");
    printf("0x%08x, 0x%04x, 0x%04x, {", g->v1, g->v2, g->v3);
    for(i=0;i<8;i++)
        printf(" 0x%02x,", g->v4[i]);
    printf("}\n");
}
#undef PRINT_IF_GUID
#endif

static void get_guid(ByteIOContext *s, GUID *g)
{
    int i;

    g->v1 = get_le32(s);
    g->v2 = get_le16(s);
    g->v3 = get_le16(s);
    for(i=0;i<8;i++)
        g->v4[i] = get_byte(s);
}

#if 0
static void get_str16(ByteIOContext *pb, char *buf, int buf_size)
{
    int len, c;
    char *q;

    len = get_le16(pb);
    q = buf;
    while (len > 0) {
        c = get_le16(pb);
        if ((q - buf) < buf_size - 1)
            *q++ = c;
        len--;
    }
    *q = '\0';
}
#endif

static void get_str16_nolen(ByteIOContext *pb, int len, char *buf, int buf_size)
{
    int c;
    char *q;

    q = buf;
    while (len > 0) {
        c = get_le16(pb);
        if ((q - buf) < buf_size - 1)
            *q++ = c;
        len-=2;
    }
    *q = '\0';
}

static int asf_probe(AVProbeData *pd)
{
    GUID g;
    const unsigned char *p;
    int i;

    /* check file header */
    if (pd->buf_size <= 32)
        return 0;
    p = pd->buf;
    g.v1 = p[0] | (p[1] << 8) | (p[2] << 16) | (p[3] << 24);
    p += 4;
    g.v2 = p[0] | (p[1] << 8);
    p += 2;
    g.v3 = p[0] | (p[1] << 8);
    p += 2;
    for(i=0;i<8;i++)
        g.v4[i] = *p++;

    if (!memcmp(&g, &asf_header, sizeof(GUID)))
        return AVPROBE_SCORE_MAX;
    else
        return 0;
}

static int asf_read_header(AVFormatContext *s, AVFormatParameters *ap)
{
    ASFContext *asf = s->priv_data;
    GUID g;
    ByteIOContext *pb = &s->pb;
    AVStream *st;
    ASFStream *asf_st;
    int size, i;
    int64_t gsize;

    get_guid(pb, &g);
    if (memcmp(&g, &asf_header, sizeof(GUID)))
        goto fail;
    get_le64(pb);
    get_le32(pb);
    get_byte(pb);
    get_byte(pb);
    memset(&asf->asfid2avid, -1, sizeof(asf->asfid2avid));
    for(;;) {
        get_guid(pb, &g);
        gsize = get_le64(pb);
#ifdef DEBUG
        printf("%08Lx: ", url_ftell(pb) - 24);
        print_guid(&g);
        printf("  size=0x%Lx\n", gsize);
#endif
        if (gsize < 24)
            goto fail;
        if (!memcmp(&g, &file_header, sizeof(GUID))) {
            get_guid(pb, &asf->hdr.guid);
            asf->hdr.file_size          = get_le64(pb);
            asf->hdr.create_time        = get_le64(pb);
            asf->hdr.packets_count      = get_le64(pb);
            asf->hdr.send_time          = get_le64(pb);
            asf->hdr.play_time          = get_le64(pb);
            asf->hdr.preroll            = get_le32(pb);
            asf->hdr.ignore             = get_le32(pb);
            asf->hdr.flags              = get_le32(pb);
            asf->hdr.min_pktsize        = get_le32(pb);
            asf->hdr.max_pktsize        = get_le32(pb);
            asf->hdr.max_bitrate        = get_le32(pb);
            asf->packet_size = asf->hdr.max_pktsize;
            asf->nb_packets = asf->hdr.packets_count;
        } else if (!memcmp(&g, &stream_header, sizeof(GUID))) {
            int type, total_size, type_specific_size, sizeX;
            unsigned int tag1;
            int64_t pos1, pos2;
            int test_for_ext_stream_audio;

            pos1 = url_ftell(pb);

            st = av_new_stream(s, 0);
            if (!st)
                goto fail;
            av_set_pts_info(st, 32, 1, 1000); /* 32 bit pts in ms */
            asf_st = av_mallocz(sizeof(ASFStream));
            if (!asf_st)
                goto fail;
            st->priv_data = asf_st;
            st->start_time = asf->hdr.preroll;
            st->duration = asf->hdr.send_time /
                (10000000 / 1000) - st->start_time;
            get_guid(pb, &g);

            test_for_ext_stream_audio = 0;
            if (!memcmp(&g, &audio_stream, sizeof(GUID))) {
                type = CODEC_TYPE_AUDIO;
            } else if (!memcmp(&g, &video_stream, sizeof(GUID))) {
                type = CODEC_TYPE_VIDEO;
            } else if (!memcmp(&g, &command_stream, sizeof(GUID))) {
                type = CODEC_TYPE_UNKNOWN;
            } else if (!memcmp(&g, &ext_stream_embed_stream_header, sizeof(GUID))) {
                test_for_ext_stream_audio = 1;
                type = CODEC_TYPE_UNKNOWN;
            } else {
                goto fail;
            }
            get_guid(pb, &g);
            total_size = get_le64(pb);
            type_specific_size = get_le32(pb);
            get_le32(pb);
            st->id = get_le16(pb) & 0x7f; /* stream id */
            // mapping of asf ID to AV stream ID;
            asf->asfid2avid[st->id] = s->nb_streams - 1;

            get_le32(pb);

            if (test_for_ext_stream_audio) {
                get_guid(pb, &g);
                if (!memcmp(&g, &ext_stream_audio_stream, sizeof(GUID))) {
                    type = CODEC_TYPE_AUDIO;
                    get_guid(pb, &g);
                    get_le32(pb);
                    get_le32(pb);
                    get_le32(pb);
                    get_guid(pb, &g);
                    get_le32(pb);
                }
            }

            st->codec->codec_type = type;
            if (type == CODEC_TYPE_AUDIO) {
                get_wav_header(pb, st->codec, type_specific_size);
                st->need_parsing = 1;
                /* We have to init the frame size at some point .... */
                pos2 = url_ftell(pb);
                if (gsize > (pos2 + 8 - pos1 + 24)) {
                    asf_st->ds_span = get_byte(pb);
                    asf_st->ds_packet_size = get_le16(pb);
                    asf_st->ds_chunk_size = get_le16(pb);
                    asf_st->ds_data_size = get_le16(pb);
                    asf_st->ds_silence_data = get_byte(pb);
                }
                //printf("Descrambling: ps:%d cs:%d ds:%d s:%d  sd:%d\n",
                //       asf_st->ds_packet_size, asf_st->ds_chunk_size,
                //       asf_st->ds_data_size, asf_st->ds_span, asf_st->ds_silence_data);
                if (asf_st->ds_span > 1) {
                    if (!asf_st->ds_chunk_size
                        || (asf_st->ds_packet_size/asf_st->ds_chunk_size <= 1))
                        asf_st->ds_span = 0; // disable descrambling
                }
                switch (st->codec->codec_id) {
                case CODEC_ID_MP3:
                    st->codec->frame_size = MPA_FRAME_SIZE;
                    break;
                case CODEC_ID_PCM_S16LE:
                case CODEC_ID_PCM_S16BE:
                case CODEC_ID_PCM_U16LE:
                case CODEC_ID_PCM_U16BE:
                case CODEC_ID_PCM_S8:
                case CODEC_ID_PCM_U8:
                case CODEC_ID_PCM_ALAW:
                case CODEC_ID_PCM_MULAW:
                    st->codec->frame_size = 1;
                    break;
                default:
                    /* This is probably wrong, but it prevents a crash later */
                    st->codec->frame_size = 1;
                    break;
                }
            } else if (type == CODEC_TYPE_VIDEO) {
                get_le32(pb);
                get_le32(pb);
                get_byte(pb);
                size = get_le16(pb); /* size */