utils.c

F:图像处理资料264264书籍ffmpeg-0.4.9-pre1VideoStream.rar 一个视频解压缩源代码

    if (!fmt) {
        err = AVERROR_NOFMT;
        goto fail;
    }
        
    /* XXX: suppress this hack for redirectors */
#ifdef CONFIG_NETWORK
    if (fmt == &redir_demux) {
        err = redir_open(ic_ptr, pb);
        url_fclose(pb);
        return err;
    }
#endif

    /* check filename in case of an image number is expected */
    if (fmt->flags & AVFMT_NEEDNUMBER) {
        if (filename_number_test(filename) < 0) { 
            err = AVERROR_NUMEXPECTED;
            goto fail;
        }
    }
    err = av_open_input_stream(ic_ptr, pb, filename, fmt, ap);
    if (err)
        goto fail;
    return 0;
 fail:
    if (file_opened)
        url_fclose(pb);
    *ic_ptr = NULL;
    return err;
    
}

/*******************************************************/

/**
 * Read a transport packet from a media file. This function is
 * absolete and should never be used. Use av_read_frame() instead.
 * 
 * @param s media file handle
 * @param pkt is filled 
 * @return 0 if OK. AVERROR_xxx if error.  
 */
int av_read_packet(AVFormatContext *s, AVPacket *pkt)
{
    return s->iformat->read_packet(s, pkt);
}

/**********************************************************/

/* get the number of samples of an audio frame. Return (-1) if error */
static int get_audio_frame_size(AVCodecContext *enc, int size)
{
    int frame_size;

    if (enc->frame_size <= 1) {
        /* specific hack for pcm codecs because no frame size is
           provided */
        switch(enc->codec_id) {
        case CODEC_ID_PCM_S16LE:
        case CODEC_ID_PCM_S16BE:
        case CODEC_ID_PCM_U16LE:
        case CODEC_ID_PCM_U16BE:
            if (enc->channels == 0)
                return -1;
            frame_size = size / (2 * enc->channels);
            break;
        case CODEC_ID_PCM_S8:
        case CODEC_ID_PCM_U8:
        case CODEC_ID_PCM_MULAW:
        case CODEC_ID_PCM_ALAW:
            if (enc->channels == 0)
                return -1;
            frame_size = size / (enc->channels);
            break;
        default:
            /* used for example by ADPCM codecs */
            if (enc->bit_rate == 0)
                return -1;
            frame_size = (size * 8 * enc->sample_rate) / enc->bit_rate;
            break;
        }
    } else {
        frame_size = enc->frame_size;
    }
    return frame_size;
}


/* return the frame duration in seconds, return 0 if not available */
static void compute_frame_duration(int *pnum, int *pden, AVStream *st, 
                                   AVCodecParserContext *pc, AVPacket *pkt)
{
    int frame_size;

    *pnum = 0;
    *pden = 0;
    switch(st->codec.codec_type) {
    case CODEC_TYPE_VIDEO:
        *pnum = st->codec.frame_rate_base;
        *pden = st->codec.frame_rate;
        if (pc && pc->repeat_pict) {
            *pden *= 2;
            *pnum = (*pnum) * (2 + pc->repeat_pict);
        }
        break;
    case CODEC_TYPE_AUDIO:
        frame_size = get_audio_frame_size(&st->codec, pkt->size);
        if (frame_size < 0)
            break;
        *pnum = frame_size;
        *pden = st->codec.sample_rate;
        break;
    default:
        break;
    }
}

static int64_t lsb2full(int64_t lsb, int64_t last_ts, int lsb_bits){
    int64_t mask = lsb_bits < 64 ? (1LL<<lsb_bits)-1 : -1LL;
    int64_t delta= last_ts - mask/2;
    return  ((lsb - delta)&mask) + delta;
}

static void compute_pkt_fields(AVFormatContext *s, AVStream *st, 
                               AVCodecParserContext *pc, AVPacket *pkt)
{
    int num, den, presentation_delayed;

    /* handle wrapping */
    if(st->cur_dts != AV_NOPTS_VALUE){
        if(pkt->pts != AV_NOPTS_VALUE)
            pkt->pts= lsb2full(pkt->pts, st->cur_dts, st->pts_wrap_bits);
        if(pkt->dts != AV_NOPTS_VALUE)
            pkt->dts= lsb2full(pkt->dts, st->cur_dts, st->pts_wrap_bits);
    }
    
    if (pkt->duration == 0) {
        compute_frame_duration(&num, &den, st, pc, pkt);
        if (den && num) {
            pkt->duration = av_rescale(1, num * (int64_t)st->time_base.den, den * (int64_t)st->time_base.num);
        }
    }

    /* do we have a video B frame ? */
    presentation_delayed = 0;
    if (st->codec.codec_type == CODEC_TYPE_VIDEO) {
        /* XXX: need has_b_frame, but cannot get it if the codec is
           not initialized */
        if ((st->codec.codec_id == CODEC_ID_MPEG1VIDEO ||
             st->codec.codec_id == CODEC_ID_MPEG2VIDEO ||
             st->codec.codec_id == CODEC_ID_MPEG4 ||
             st->codec.codec_id == CODEC_ID_H264) && 
            pc && pc->pict_type != FF_B_TYPE)
            presentation_delayed = 1;
        /* this may be redundant, but it shouldnt hurt */
        if(pkt->dts != AV_NOPTS_VALUE && pkt->pts != AV_NOPTS_VALUE && pkt->pts > pkt->dts)
            presentation_delayed = 1;
    }
    
    if(st->cur_dts == AV_NOPTS_VALUE){
        if(presentation_delayed) st->cur_dts = -pkt->duration;
        else                     st->cur_dts = 0;
    }

//    av_log(NULL, AV_LOG_DEBUG, "IN delayed:%d pts:%lld, dts:%lld cur_dts:%lld st:%d pc:%p\n", presentation_delayed, pkt->pts, pkt->dts, st->cur_dts, pkt->stream_index, pc);
    /* interpolate PTS and DTS if they are not present */
    if (presentation_delayed) {
        /* DTS = decompression time stamp */
        /* PTS = presentation time stamp */
        if (pkt->dts == AV_NOPTS_VALUE) {
            /* if we know the last pts, use it */
            if(st->last_IP_pts != AV_NOPTS_VALUE)
                st->cur_dts = pkt->dts = st->last_IP_pts;
            else
                pkt->dts = st->cur_dts;
        } else {
            st->cur_dts = pkt->dts;
        }
        /* this is tricky: the dts must be incremented by the duration
           of the frame we are displaying, i.e. the last I or P frame */
        if (st->last_IP_duration == 0)
            st->cur_dts += pkt->duration;
        else
            st->cur_dts += st->last_IP_duration;
        st->last_IP_duration  = pkt->duration;
        st->last_IP_pts= pkt->pts;
        /* cannot compute PTS if not present (we can compute it only
           by knowing the futur */
    } else {
        /* presentation is not delayed : PTS and DTS are the same */
        if (pkt->pts == AV_NOPTS_VALUE) {
            if (pkt->dts == AV_NOPTS_VALUE) {
                pkt->pts = st->cur_dts;
                pkt->dts = st->cur_dts;
            }
            else {
                st->cur_dts = pkt->dts;
                pkt->pts = pkt->dts;
            }
        } else {
            st->cur_dts = pkt->pts;
            pkt->dts = pkt->pts;
        }
        st->cur_dts += pkt->duration;
    }
//    av_log(NULL, AV_LOG_DEBUG, "OUTdelayed:%d pts:%lld, dts:%lld cur_dts:%lld\n", presentation_delayed, pkt->pts, pkt->dts, st->cur_dts);
    
    /* update flags */
    if (pc) {
        pkt->flags = 0;
        /* key frame computation */
        switch(st->codec.codec_type) {
        case CODEC_TYPE_VIDEO:
            if (pc->pict_type == FF_I_TYPE)
                pkt->flags |= PKT_FLAG_KEY;
            break;
        case CODEC_TYPE_AUDIO:
            pkt->flags |= PKT_FLAG_KEY;
            break;
        default:
            break;
        }
    }

    /* convert the packet time stamp units */
    if(pkt->pts != AV_NOPTS_VALUE)
        pkt->pts = av_rescale(pkt->pts, AV_TIME_BASE * (int64_t)st->time_base.num, st->time_base.den);
    if(pkt->dts != AV_NOPTS_VALUE)
        pkt->dts = av_rescale(pkt->dts, AV_TIME_BASE * (int64_t)st->time_base.num, st->time_base.den);

    /* duration field */
    pkt->duration = av_rescale(pkt->duration, AV_TIME_BASE * (int64_t)st->time_base.num, st->time_base.den);
}

static void av_destruct_packet_nofree(AVPacket *pkt)
{
    pkt->data = NULL; pkt->size = 0;
}

static int av_read_frame_internal(AVFormatContext *s, AVPacket *pkt)
{
    AVStream *st;
    int len, ret, i;

    for(;;) {
        /* select current input stream component */
        st = s->cur_st;
        if (st) {
            if (!st->parser) {
                /* no parsing needed: we just output the packet as is */
                /* raw data support */
                *pkt = s->cur_pkt;
                compute_pkt_fields(s, st, NULL, pkt);
                s->cur_st = NULL;
                return 0;
            } else if (s->cur_len > 0) {
                len = av_parser_parse(st->parser, &st->codec, &pkt->data, &pkt->size, 
                                      s->cur_ptr, s->cur_len,
                                      s->cur_pkt.pts, s->cur_pkt.dts);
                s->cur_pkt.pts = AV_NOPTS_VALUE;
                s->cur_pkt.dts = AV_NOPTS_VALUE;
                /* increment read pointer */
                s->cur_ptr += len;
                s->cur_len -= len;
                
                /* return packet if any */
                if (pkt->size) {
                got_packet:
                    pkt->duration = 0;
                    pkt->stream_index = st->index;
                    pkt->pts = st->parser->pts;
                    pkt->dts = st->parser->dts;
                    pkt->destruct = av_destruct_packet_nofree;
                    compute_pkt_fields(s, st, st->parser, pkt);
                    return 0;
                }
            } else {
                /* free packet */
                av_free_packet(&s->cur_pkt); 
                s->cur_st = NULL;
            }
        } else {
            /* read next packet */
            ret = av_read_packet(s, &s->cur_pkt);
            if (ret < 0) {
                if (ret == -EAGAIN)
                    return ret;
                /* return the last frames, if any */
                for(i = 0; i < s->nb_streams; i++) {
                    st = s->streams[i];
                    if (st->parser) {
                        av_parser_parse(st->parser, &st->codec, 
                                        &pkt->data, &pkt->size, 
                                        NULL, 0, 
                                        AV_NOPTS_VALUE, AV_NOPTS_VALUE);
                        if (pkt->size)
                            goto got_packet;
                    }
                }
                /* no more packets: really terminates parsing */
                return ret;
            }
            
            st = s->streams[s->cur_pkt.stream_index];

            s->cur_st = st;
            s->cur_ptr = s->cur_pkt.data;
            s->cur_len = s->cur_pkt.size;
            if (st->need_parsing && !st->parser) {
                st->parser = av_parser_init(st->codec.codec_id);
                if (!st->parser) {
                    /* no parser available : just output the raw packets */
                    st->need_parsing = 0;
                }
            }
        }
    }
}

/**
 * Return the next frame of a stream. The returned packet is valid
 * until the next av_read_frame() or until av_close_input_file() and
 * must be freed with av_free_packet. For video, the packet contains
 * exactly one frame. For audio, it contains an integer number of
 * frames if each frame has a known fixed size (e.g. PCM or ADPCM
 * data). If the audio frames have a variable size (e.g. MPEG audio),
 * then it contains one frame.
 * 
 * pkt->pts, pkt->dts and pkt->duration are always set to correct
 * values in AV_TIME_BASE unit (and guessed if the format cannot
 * provided them). pkt->pts can be AV_NOPTS_VALUE if the video format
 * has B frames, so it is better to rely on pkt->dts if you do not
 * decompress the payload.
 * 
 * Return 0 if OK, < 0 if error or end of file.  
 */
int av_read_frame(AVFormatContext *s, AVPacket *pkt)
{
    AVPacketList *pktl;

    pktl = s->packet_buffer;
    if (pktl) {
        /* read packet from packet buffer, if there is data */
        *pkt = pktl->pkt;
        s->packet_buffer = pktl->next;
        av_free(pktl);
        return 0;
    } else {
        return av_read_frame_internal(s, pkt);
    }
}

/* XXX: suppress the packet queue */
static void flush_packet_queue(AVFormatContext *s)
{
    AVPacketList *pktl;

    for(;;) {
        pktl = s->packet_buffer;
        if (!pktl) 
            break;
        s->packet_buffer = pktl->next;
        av_free_packet(&pktl->pkt);
        av_free(pktl);
    }
}

/*******************************************************/
/* seek support */

int av_find_default_stream_index(AVFormatContext *s)
{
    int i;
    AVStream *st;

    if (s->nb_streams <= 0)
        return -1;
    for(i = 0; i < s->nb_streams; i++) {
        st = s->streams[i];
        if (st->codec.codec_type == CODEC_TYPE_VIDEO) {
            return i;
        }
    }
    return 0;
}

/* flush the frame reader */
static void av_read_frame_flush(AVFormatContext *s)
{
    AVStream *st;
    int i;

    flush_packet_queue(s);

    /* free previous packet */
    if (s->cur_st) {
        if (s->cur_st->parser)
            av_free_packet(&s->cur_pkt);
        s->cur_st = NULL;
    }
    /* fail safe */
    s->cur_ptr = NULL;
    s->cur_len = 0;
    
    /* for each stream, reset read state */
    for(i = 0; i < s->nb_streams; i++) {
        st = s->streams[i];
        
        if (st->parser) {
            av_parser_close(st->parser);
            st->parser = NULL;
        }
        st->last_IP_pts = AV_NOPTS_VALUE;
        st->cur_dts = 0; /* we set the current DTS to an unspecified origin */
    }
}

/**
 * add a index entry into a sorted list updateing if it is already there.
 * @param timestamp timestamp in the timebase of the given stream
 */
int av_add_index_entry(AVStream *st,
                            int64_t pos, int64_t timestamp, int distance, int flags)
{
    AVIndexEntry *entries, *ie;
    int index;
    
    entries = av_fast_realloc(st->index_entries,
                              &st->index_entries_allocated_size,
                              (st->nb_index_entries + 1) * 
                              sizeof(AVIndexEntry));
    st->index_entries= entries;

    if(st->nb_index_entries){
        index= av_index_search_timestamp(st, timestamp);
        ie= &entries[index];

        if(ie->timestamp != timestamp){
            if(ie->timestamp < timestamp){