FFmpeg/libavformat/swf.c

/*
 * Flash Compatible Streaming Format
 * Copyright (c) 2000 Fabrice Bellard.
 * Copyright (c) 2003 Tinic Uro.
 *
 * 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 "bitstream.h"
#include "riff.h"    /* for CodecTag */

/* should have a generic way to indicate probable size */
#define DUMMY_FILE_SIZE   (100 * 1024 * 1024)
#define DUMMY_DURATION    600 /* in seconds */

#define TAG_END           0
#define TAG_SHOWFRAME     1
#define TAG_DEFINESHAPE   2
#define TAG_FREECHARACTER 3
#define TAG_PLACEOBJECT   4
#define TAG_REMOVEOBJECT  5
#define TAG_STREAMHEAD    18
#define TAG_STREAMBLOCK   19
#define TAG_JPEG2         21
#define TAG_PLACEOBJECT2  26
#define TAG_STREAMHEAD2   45
#define TAG_VIDEOSTREAM   60
#define TAG_VIDEOFRAME    61

#define TAG_LONG         0x100

/* flags for shape definition */
#define FLAG_MOVETO      0x01
#define FLAG_SETFILL0    0x02
#define FLAG_SETFILL1    0x04

#define AUDIO_FIFO_SIZE 65536

/* character id used */
#define BITMAP_ID 0
#define VIDEO_ID 0
#define SHAPE_ID  1

#undef NDEBUG
#include <assert.h>

typedef struct {
    int audio_stream_index;
    offset_t duration_pos;
    offset_t tag_pos;

    int samples_per_frame;
    int sound_samples;
    int swf_frame_number;
    int video_frame_number;
    int frame_rate;
    int tag;

    uint8_t audio_fifo[AUDIO_FIFO_SIZE];
    int audio_in_pos;

    int video_type;
    int audio_type;
} SWFContext;

static const AVCodecTag swf_codec_tags[] = {
    {CODEC_ID_FLV1, 0x02},
    {CODEC_ID_VP6F, 0x04},
    {0, 0},
};

static const AVCodecTag swf_audio_codec_tags[] = {
    {CODEC_ID_PCM_S16LE,  0x00},
    {CODEC_ID_ADPCM_SWF,  0x01},
    {CODEC_ID_MP3,        0x02},
    {CODEC_ID_PCM_S16LE,  0x03},
  //{CODEC_ID_NELLYMOSER, 0x06},
    {0, 0},
};

#ifdef CONFIG_MUXERS
static void put_swf_tag(AVFormatContext *s, int tag)
{
    SWFContext *swf = s->priv_data;
    ByteIOContext *pb = &s->pb;

    swf->tag_pos = url_ftell(pb);
    swf->tag = tag;
    /* reserve some room for the tag */
    if (tag & TAG_LONG) {
        put_le16(pb, 0);
        put_le32(pb, 0);
    } else {
        put_le16(pb, 0);
    }
}

static void put_swf_end_tag(AVFormatContext *s)
{
    SWFContext *swf = s->priv_data;
    ByteIOContext *pb = &s->pb;
    offset_t pos;
    int tag_len, tag;

    pos = url_ftell(pb);
    tag_len = pos - swf->tag_pos - 2;
    tag = swf->tag;
    url_fseek(pb, swf->tag_pos, SEEK_SET);
    if (tag & TAG_LONG) {
        tag &= ~TAG_LONG;
        put_le16(pb, (tag << 6) | 0x3f);
        put_le32(pb, tag_len - 4);
    } else {
        assert(tag_len < 0x3f);
        put_le16(pb, (tag << 6) | tag_len);
    }
    url_fseek(pb, pos, SEEK_SET);
}

static inline void max_nbits(int *nbits_ptr, int val)
{
    int n;

    if (val == 0)
        return;
    val = abs(val);
    n = 1;
    while (val != 0) {
        n++;
        val >>= 1;
    }
    if (n > *nbits_ptr)
        *nbits_ptr = n;
}

static void put_swf_rect(ByteIOContext *pb,
                         int xmin, int xmax, int ymin, int ymax)
{
    PutBitContext p;
    uint8_t buf[256];
    int nbits, mask;

    init_put_bits(&p, buf, sizeof(buf));

    nbits = 0;
    max_nbits(&nbits, xmin);
    max_nbits(&nbits, xmax);
    max_nbits(&nbits, ymin);
    max_nbits(&nbits, ymax);
    mask = (1 << nbits) - 1;

    /* rectangle info */
    put_bits(&p, 5, nbits);
    put_bits(&p, nbits, xmin & mask);
    put_bits(&p, nbits, xmax & mask);
    put_bits(&p, nbits, ymin & mask);
    put_bits(&p, nbits, ymax & mask);

    flush_put_bits(&p);
    put_buffer(pb, buf, pbBufPtr(&p) - p.buf);
}

static void put_swf_line_edge(PutBitContext *pb, int dx, int dy)
{
    int nbits, mask;

    put_bits(pb, 1, 1); /* edge */
    put_bits(pb, 1, 1); /* line select */
    nbits = 2;
    max_nbits(&nbits, dx);
    max_nbits(&nbits, dy);

    mask = (1 << nbits) - 1;
    put_bits(pb, 4, nbits - 2); /* 16 bits precision */
    if (dx == 0) {
      put_bits(pb, 1, 0);
      put_bits(pb, 1, 1);
      put_bits(pb, nbits, dy & mask);
    } else if (dy == 0) {
      put_bits(pb, 1, 0);
      put_bits(pb, 1, 0);
      put_bits(pb, nbits, dx & mask);
    } else {
      put_bits(pb, 1, 1);
      put_bits(pb, nbits, dx & mask);
      put_bits(pb, nbits, dy & mask);
    }
}

#define FRAC_BITS 16

/* put matrix */
static void put_swf_matrix(ByteIOContext *pb,
                           int a, int b, int c, int d, int tx, int ty)
{
    PutBitContext p;
    uint8_t buf[256];
    int nbits;

    init_put_bits(&p, buf, sizeof(buf));

    put_bits(&p, 1, 1); /* a, d present */
    nbits = 1;
    max_nbits(&nbits, a);
    max_nbits(&nbits, d);
    put_bits(&p, 5, nbits); /* nb bits */
    put_bits(&p, nbits, a);
    put_bits(&p, nbits, d);

    put_bits(&p, 1, 1); /* b, c present */
    nbits = 1;
    max_nbits(&nbits, c);
    max_nbits(&nbits, b);
    put_bits(&p, 5, nbits); /* nb bits */
    put_bits(&p, nbits, c);
    put_bits(&p, nbits, b);

    nbits = 1;
    max_nbits(&nbits, tx);
    max_nbits(&nbits, ty);
    put_bits(&p, 5, nbits); /* nb bits */
    put_bits(&p, nbits, tx);
    put_bits(&p, nbits, ty);

    flush_put_bits(&p);
    put_buffer(pb, buf, pbBufPtr(&p) - p.buf);
}

/* */
static int swf_write_header(AVFormatContext *s)
{
    SWFContext *swf = s->priv_data;
    ByteIOContext *pb = &s->pb;
    AVCodecContext *enc, *audio_enc, *video_enc;
    PutBitContext p;
    uint8_t buf1[256];
    int i, width, height, rate, rate_base;

    swf->audio_in_pos = 0;
    swf->sound_samples = 0;
    swf->swf_frame_number = 0;
    swf->video_frame_number = 0;

    video_enc = NULL;
    audio_enc = NULL;
    for(i=0;i<s->nb_streams;i++) {
        enc = s->streams[i]->codec;
        if (enc->codec_type == CODEC_TYPE_AUDIO) {
            if (enc->codec_id == CODEC_ID_MP3) {
                if (!enc->frame_size) {
                    av_log(s, AV_LOG_ERROR, "audio frame size not set\n");
                    return -1;
                }
                audio_enc = enc;
            } else {
                av_log(s, AV_LOG_ERROR, "SWF muxer only supports MP3\n");
                return -1;
            }
        } else {
            if ( enc->codec_id == CODEC_ID_VP6F ||
                 enc->codec_id == CODEC_ID_FLV1 ||
                 enc->codec_id == CODEC_ID_MJPEG ) {
                video_enc = enc;
            } else {
                av_log(s, AV_LOG_ERROR, "SWF muxer only supports VP6, FLV1 and MJPEG\n");
                return -1;
            }
        }
    }

    if (!video_enc) {
        /* currenty, cannot work correctly if audio only */
        swf->video_type = 0;
        width = 320;
        height = 200;
        rate = 10;
        rate_base= 1;
    } else {
        swf->video_type = video_enc->codec_id;
        width = video_enc->width;
        height = video_enc->height;
        rate = video_enc->time_base.den;
        rate_base = video_enc->time_base.num;
    }

    if (!audio_enc ) {
        swf->audio_type = 0;
        swf->samples_per_frame = ( 44100. * rate_base ) / rate;
    } else {
        swf->audio_type = audio_enc->codec_id;
        swf->samples_per_frame = ( ( audio_enc->sample_rate ) * rate_base ) / rate;
    }

    put_tag(pb, "FWS");
    if ( video_enc && video_enc->codec_id == CODEC_ID_VP6F ) {
        put_byte(pb, 8); /* version (version 8 and above support VP6 codec) */
    } else if ( video_enc && video_enc->codec_id == CODEC_ID_FLV1 ) {
        put_byte(pb, 6); /* version (version 6 and above support FLV1 codec) */
    } else {
        put_byte(pb, 4); /* version (should use 4 for mpeg audio support) */
    }
    put_le32(pb, DUMMY_FILE_SIZE); /* dummy size
                                      (will be patched if not streamed) */

    put_swf_rect(pb, 0, width * 20, 0, height * 20);
    put_le16(pb, (rate * 256) / rate_base); /* frame rate */
    swf->duration_pos = url_ftell(pb);
    put_le16(pb, (uint16_t)(DUMMY_DURATION * (int64_t)rate / rate_base)); /* frame count */

    /* define a shape with the jpeg inside */
    if ( video_enc && (video_enc->codec_id == CODEC_ID_VP6F ||
                       video_enc->codec_id == CODEC_ID_FLV1 )) {
    } else if ( video_enc && video_enc->codec_id == CODEC_ID_MJPEG ) {
        put_swf_tag(s, TAG_DEFINESHAPE);

        put_le16(pb, SHAPE_ID); /* ID of shape */
        /* bounding rectangle */
        put_swf_rect(pb, 0, width, 0, height);
        /* style info */
        put_byte(pb, 1); /* one fill style */
        put_byte(pb, 0x41); /* clipped bitmap fill */
        put_le16(pb, BITMAP_ID); /* bitmap ID */
        /* position of the bitmap */
        put_swf_matrix(pb, (int)(1.0 * (1 << FRAC_BITS)), 0,
                        0, (int)(1.0 * (1 << FRAC_BITS)), 0, 0);
        put_byte(pb, 0); /* no line style */

        /* shape drawing */
        init_put_bits(&p, buf1, sizeof(buf1));
        put_bits(&p, 4, 1); /* one fill bit */
        put_bits(&p, 4, 0); /* zero line bit */

        put_bits(&p, 1, 0); /* not an edge */
        put_bits(&p, 5, FLAG_MOVETO | FLAG_SETFILL0);
        put_bits(&p, 5, 1); /* nbits */
        put_bits(&p, 1, 0); /* X */
        put_bits(&p, 1, 0); /* Y */
        put_bits(&p, 1, 1); /* set fill style 1 */

        /* draw the rectangle ! */
        put_swf_line_edge(&p, width, 0);
        put_swf_line_edge(&p, 0, height);
        put_swf_line_edge(&p, -width, 0);
        put_swf_line_edge(&p, 0, -height);

        /* end of shape */
        put_bits(&p, 1, 0); /* not an edge */
        put_bits(&p, 5, 0);

        flush_put_bits(&p);
        put_buffer(pb, buf1, pbBufPtr(&p) - p.buf);

        put_swf_end_tag(s);
    }

    if (audio_enc && audio_enc->codec_id == CODEC_ID_MP3 ) {
        int v;

        /* start sound */
        put_swf_tag(s, TAG_STREAMHEAD2);

        v = 0;
        switch(audio_enc->sample_rate) {
        case 11025:
            v |= 1 << 2;
            break;
        case 22050:
            v |= 2 << 2;
            break;
        case 44100:
            v |= 3 << 2;
            break;
        default:
            /* not supported */
            av_log(s, AV_LOG_ERROR, "swf doesnt support that sample rate, choose from (44100, 22050, 11025)\n");
            return -1;
        }
        v |= 0x02; /* 16 bit playback */
        if (audio_enc->channels == 2)
            v |= 0x01; /* stereo playback */
        put_byte(&s->pb, v);
        v |= 0x20; /* mp3 compressed */
        put_byte(&s->pb, v);
        put_le16(&s->pb, swf->samples_per_frame);  /* avg samples per frame */
        put_le16(&s->pb, 0);

        put_swf_end_tag(s);
    }

    put_flush_packet(&s->pb);
    return 0;
}

static int swf_write_video(AVFormatContext *s,
                           AVCodecContext *enc, const uint8_t *buf, int size)
{
    SWFContext *swf = s->priv_data;
    ByteIOContext *pb = &s->pb;

    /* Flash Player limit */
    if ( swf->swf_frame_number == 16000 ) {
        av_log(enc, AV_LOG_INFO, "warning: Flash Player limit of 16000 frames reached\n");
    }

            if ( swf->video_type == CODEC_ID_VP6F ||
                 swf->video_type == CODEC_ID_FLV1 ) {
                if ( swf->video_frame_number == 0 ) {
                    /* create a new video object */
                    put_swf_tag(s, TAG_VIDEOSTREAM);
                    put_le16(pb, VIDEO_ID);
                    put_le16(pb, 15000 ); /* hard flash player limit */
                    put_le16(pb, enc->width);
                    put_le16(pb, enc->height);
                    put_byte(pb, 0);
                    put_byte(pb,codec_get_tag(swf_codec_tags,swf->video_type));
                    put_swf_end_tag(s);

                    /* place the video object for the first time */
                    put_swf_tag(s, TAG_PLACEOBJECT2);
                    put_byte(pb, 0x36);
                    put_le16(pb, 1);
                    put_le16(pb, VIDEO_ID);
                    put_swf_matrix(pb, 1 << FRAC_BITS, 0, 0, 1 << FRAC_BITS, 0, 0);
                    put_le16(pb, swf->video_frame_number );
                    put_byte(pb, 'v');
                    put_byte(pb, 'i');
                    put_byte(pb, 'd');
                    put_byte(pb, 'e');
                    put_byte(pb, 'o');
                    put_byte(pb, 0x00);
                    put_swf_end_tag(s);
                } else {
                    /* mark the character for update */
                    put_swf_tag(s, TAG_PLACEOBJECT2);
                    put_byte(pb, 0x11);
                    put_le16(pb, 1);
                    put_le16(pb, swf->video_frame_number );
                    put_swf_end_tag(s);
                }

                    /* set video frame data */
                    put_swf_tag(s, TAG_VIDEOFRAME | TAG_LONG);
                    put_le16(pb, VIDEO_ID);
                    put_le16(pb, swf->video_frame_number++ );
                    put_buffer(pb, buf, size);
                    put_swf_end_tag(s);
            } else if ( swf->video_type == CODEC_ID_MJPEG ) {
                if (swf->swf_frame_number > 0) {
                    /* remove the shape */
                    put_swf_tag(s, TAG_REMOVEOBJECT);
                    put_le16(pb, SHAPE_ID); /* shape ID */
                    put_le16(pb, 1); /* depth */
                    put_swf_end_tag(s);

                    /* free the bitmap */
                    put_swf_tag(s, TAG_FREECHARACTER);
                    put_le16(pb, BITMAP_ID);
                    put_swf_end_tag(s);
                }

                put_swf_tag(s, TAG_JPEG2 | TAG_LONG);

                put_le16(pb, BITMAP_ID); /* ID of the image */

                /* a dummy jpeg header seems to be required */
                put_byte(pb, 0xff);
                put_byte(pb, 0xd8);
                put_byte(pb, 0xff);
                put_byte(pb, 0xd9);
                /* write the jpeg image */
                put_buffer(pb, buf, size);

                put_swf_end_tag(s);

                /* draw the shape */

                put_swf_tag(s, TAG_PLACEOBJECT);
                put_le16(pb, SHAPE_ID); /* shape ID */
                put_le16(pb, 1); /* depth */
                put_swf_matrix(pb, 20 << FRAC_BITS, 0, 0, 20 << FRAC_BITS, 0, 0);
                put_swf_end_tag(s);
            } else {
                /* invalid codec */
            }

            swf->swf_frame_number ++;

    /* streaming sound always should be placed just before showframe tags */
    if (swf->audio_type && swf->audio_in_pos) {
        put_swf_tag(s, TAG_STREAMBLOCK | TAG_LONG);
        put_le16(pb, swf->sound_samples);
        put_le16(pb, 0); // seek samples
        put_buffer(pb, swf->audio_fifo, swf->audio_in_pos);
        put_swf_end_tag(s);

        /* update FIFO */
        swf->sound_samples = 0;
        swf->audio_in_pos = 0;
    }

    /* output the frame */
    put_swf_tag(s, TAG_SHOWFRAME);
    put_swf_end_tag(s);

    put_flush_packet(&s->pb);

    return 0;
}

static int swf_write_audio(AVFormatContext *s,
                           AVCodecContext *enc, const uint8_t *buf, int size)
{
    SWFContext *swf = s->priv_data;

    /* Flash Player limit */
    if ( swf->swf_frame_number == 16000 ) {
        av_log(enc, AV_LOG_INFO, "warning: Flash Player limit of 16000 frames reached\n");
    }

    if (swf->audio_in_pos + size >= AUDIO_FIFO_SIZE) {
        av_log(s, AV_LOG_ERROR, "audio fifo too small to mux audio essence\n");
        return -1;
    }

    memcpy(swf->audio_fifo +  swf->audio_in_pos, buf, size);
    swf->audio_in_pos += size;
    swf->sound_samples += enc->frame_size;

    /* if audio only stream make sure we add swf frames */
    if ( swf->video_type == 0 ) {
        swf_write_video(s, enc, 0, 0);
    }

    return 0;
}

static int swf_write_packet(AVFormatContext *s, AVPacket *pkt)
{
    AVCodecContext *codec = s->streams[pkt->stream_index]->codec;
    if (codec->codec_type == CODEC_TYPE_AUDIO)
        return swf_write_audio(s, codec, pkt->data, pkt->size);
    else
        return swf_write_video(s, codec, pkt->data, pkt->size);
}

static int swf_write_trailer(AVFormatContext *s)
{
    SWFContext *swf = s->priv_data;
    ByteIOContext *pb = &s->pb;
    AVCodecContext *enc, *video_enc;
    int file_size, i;

    video_enc = NULL;
    for(i=0;i<s->nb_streams;i++) {
        enc = s->streams[i]->codec;
        if (enc->codec_type == CODEC_TYPE_VIDEO)
            video_enc = enc;
    }

    put_swf_tag(s, TAG_END);
    put_swf_end_tag(s);

    put_flush_packet(&s->pb);

    /* patch file size and number of frames if not streamed */
    if (!url_is_streamed(&s->pb) && video_enc) {
        file_size = url_ftell(pb);
        url_fseek(pb, 4, SEEK_SET);
        put_le32(pb, file_size);
        url_fseek(pb, swf->duration_pos, SEEK_SET);
        put_le16(pb, video_enc->frame_number);
        url_fseek(pb, file_size, SEEK_SET);
    }
    return 0;
}
#endif //CONFIG_MUXERS

/*********************************************/
/* Extract FLV encoded frame and MP3 from swf
   Note that the detection of the real frame
   is inaccurate at this point as it can be
   quite tricky to determine, you almost certainly
   will get a bad audio/video sync */

static int get_swf_tag(ByteIOContext *pb, int *len_ptr)
{
    int tag, len;

    if (url_feof(pb))
        return -1;

    tag = get_le16(pb);
    len = tag & 0x3f;
    tag = tag >> 6;
    if (len == 0x3f) {
        len = get_le32(pb);
    }
//    av_log(NULL, AV_LOG_DEBUG, "Tag: %d - Len: %d\n", tag, len);
    *len_ptr = len;
    return tag;
}


static int swf_probe(AVProbeData *p)
{
    /* check file header */
    if ((p->buf[0] == 'F' || p->buf[0] == 'C') && p->buf[1] == 'W' &&
        p->buf[2] == 'S')
        return AVPROBE_SCORE_MAX;
    else
        return 0;
}

static int swf_read_header(AVFormatContext *s, AVFormatParameters *ap)
{
    SWFContext *swf = s->priv_data;
    ByteIOContext *pb = &s->pb;
    int nbits, len, tag, v;
    offset_t frame_offset = -1;
    AVStream *ast = 0;
    AVStream *vst = 0;

    tag = get_be32(pb) & 0xffffff00;

    if (tag == MKBETAG('C', 'W', 'S', 0))
    {
        av_log(s, AV_LOG_ERROR, "Compressed SWF format not supported\n");
        return AVERROR_IO;
    }
    if (tag != MKBETAG('F', 'W', 'S', 0))
        return AVERROR_IO;
    get_le32(pb);
    /* skip rectangle size */
    nbits = get_byte(pb) >> 3;
    len = (4 * nbits - 3 + 7) / 8;
    url_fskip(pb, len);
    swf->frame_rate = get_le16(pb); /* 8.8 fixed */
    get_le16(pb); /* frame count */

    swf->samples_per_frame = 0;

    for(;;) {
        offset_t tag_offset = url_ftell(pb);
        tag = get_swf_tag(pb, &len);
        if (tag < 0 || tag == TAG_VIDEOFRAME || tag == TAG_STREAMBLOCK) {
            url_fseek(pb, frame_offset == -1 ? tag_offset : frame_offset, SEEK_SET);
            break;
        }
        if ( tag == TAG_VIDEOSTREAM && !vst) {
            int ch_id = get_le16(pb);
            get_le16(pb);
            get_le16(pb);
            get_le16(pb);
            get_byte(pb);
            /* Check for FLV1 */
            vst = av_new_stream(s, ch_id);
            vst->codec->codec_type = CODEC_TYPE_VIDEO;
            vst->codec->codec_id = codec_get_id(swf_codec_tags, get_byte(pb));
        } else if ( ( tag == TAG_STREAMHEAD || tag == TAG_STREAMHEAD2 ) && !ast) {
            /* streaming found */
            int sample_rate_code;
            get_byte(pb);
            v = get_byte(pb);
            swf->samples_per_frame = get_le16(pb);
            ast = av_new_stream(s, -1); /* -1 to avoid clash with video stream ch_id */
            swf->audio_stream_index = ast->index;
            ast->codec->channels = 1 + (v&1);
            ast->codec->codec_type = CODEC_TYPE_AUDIO;
            ast->codec->codec_id = codec_get_id(swf_audio_codec_tags, (v>>4) & 15);
            ast->need_parsing = AVSTREAM_PARSE_FULL;
            sample_rate_code= (v>>2) & 3;
            if (!sample_rate_code)
                return AVERROR_IO;
            ast->codec->sample_rate = 11025 << (sample_rate_code-1);
            av_set_pts_info(ast, 64, 1, ast->codec->sample_rate);
            if (len > 4)
                url_fskip(pb,len-4);

        } else if (tag == TAG_JPEG2 && !vst) {
            vst = av_new_stream(s, -2); /* -2 to avoid clash with video stream and audio stream */
            vst->codec->codec_type = CODEC_TYPE_VIDEO;
            vst->codec->codec_id = CODEC_ID_MJPEG;
            url_fskip(pb, len);
            frame_offset = tag_offset;
        } else {
            url_fskip(pb, len);
        }
    }
    if (vst)
        av_set_pts_info(vst, 64, 256, swf->frame_rate);
    return 0;
}

static int swf_read_packet(AVFormatContext *s, AVPacket *pkt)
{
    SWFContext *swf = s->priv_data;
    ByteIOContext *pb = &s->pb;
    AVStream *st = 0;
    int tag, len, i, frame;

    for(;;) {
        tag = get_swf_tag(pb, &len);
        if (tag < 0)
            return AVERROR_IO;
        if (tag == TAG_VIDEOFRAME) {
            int ch_id = get_le16(pb);
            len -= 2;
            for( i=0; i<s->nb_streams; i++ ) {
                st = s->streams[i];
                if (st->codec->codec_type == CODEC_TYPE_VIDEO && st->id == ch_id) {
                    frame = get_le16(pb);
                    av_get_packet(pb, pkt, len-2);
                    pkt->pts = frame;
                    pkt->stream_index = st->index;
                    return pkt->size;
                }
            }
        } else if (tag == TAG_STREAMBLOCK) {
            st = s->streams[swf->audio_stream_index];
            if (st->codec->codec_id == CODEC_ID_MP3) {
                url_fskip(pb, 4);
                av_get_packet(pb, pkt, len-4);
            } else { // ADPCM, PCM
                av_get_packet(pb, pkt, len);
            }
            pkt->stream_index = st->index;
            return pkt->size;
        } else if (tag == TAG_JPEG2) {
            for (i=0; i<s->nb_streams; i++) {
                st = s->streams[i];
                if (st->id == -2) {
                    get_le16(pb); /* BITMAP_ID */
                    av_new_packet(pkt, len-2);
                    get_buffer(pb, pkt->data, 4);
                    if (AV_RB32(pkt->data) == 0xffd8ffd9) {
                        /* old SWF files containing SOI/EOI as data start */
                        pkt->size -= 4;
                        get_buffer(pb, pkt->data, pkt->size);
                    } else {
                        get_buffer(pb, pkt->data + 4, pkt->size - 4);
                    }
                    pkt->stream_index = st->index;
                    return pkt->size;
                }
            }
        }
        url_fskip(pb, len);
    }
    return 0;
}

static int swf_read_close(AVFormatContext *s)
{
     return 0;
}

#ifdef CONFIG_SWF_DEMUXER
AVInputFormat swf_demuxer = {
    "swf",
    "Flash format",
    sizeof(SWFContext),
    swf_probe,
    swf_read_header,
    swf_read_packet,
    swf_read_close,
};
#endif
#ifdef CONFIG_SWF_MUXER
AVOutputFormat swf_muxer = {
    "swf",
    "Flash format",
    "application/x-shockwave-flash",
    "swf",
    sizeof(SWFContext),
    CODEC_ID_MP3,
    CODEC_ID_FLV1,
    swf_write_header,
    swf_write_packet,
    swf_write_trailer,
};
#endif