utils.c

ffmpeg源码分析

/*
 * Various utilities for ffmpeg system
 * Copyright (c) 2000, 2001, 2002 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"

#undef NDEBUG
#include <assert.h>

/**
 * @file libavformat/utils.c
 * Various utility functions for using ffmpeg library.
 */

/** head of registered input format linked list. */
AVInputFormat *first_iformat = NULL;
/** head of registered output format linked list. */
AVOutputFormat *first_oformat = NULL;
/** head of registered image format linked list. */
AVImageFormat *first_image_format = NULL;

void av_register_input_format(AVInputFormat *format)
{
    AVInputFormat **p;
    p = &first_iformat;
    while (*p != NULL) p = &(*p)->next;
    *p = format;
    format->next = NULL;
}

void av_register_output_format(AVOutputFormat *format)
{
    AVOutputFormat **p;
    p = &first_oformat;
    while (*p != NULL) p = &(*p)->next;
    *p = format;
    format->next = NULL;
}

int match_ext(const char *filename, const char *extensions)
{
    const char *ext, *p;
    char ext1[32], *q;

    if(!filename)
        return 0;

    ext = strrchr(filename, '.');
    if (ext) {
        ext++;
        p = extensions;
        for(;;) {
            q = ext1;
            while (*p != '\0' && *p != ',' && q-ext1<sizeof(ext1)-1)
                *q++ = *p++;
            *q = '\0';
            if (!strcasecmp(ext1, ext))
                return 1;
            if (*p == '\0')
                break;
            p++;
        }
    }
    return 0;
}

AVOutputFormat *guess_format(const char *short_name, const char *filename,
                             const char *mime_type)
{
    AVOutputFormat *fmt, *fmt_found;
    int score_max, score;

    /* specific test for image sequences */
    if (!short_name && filename &&
        filename_number_test(filename) >= 0 &&
        av_guess_image2_codec(filename) != CODEC_ID_NONE) {
        return guess_format("image2", NULL, NULL);
    }
    if (!short_name && filename &&
        filename_number_test(filename) >= 0 &&
        guess_image_format(filename)) {
        return guess_format("image", NULL, NULL);
    }

    /* find the proper file type */
    fmt_found = NULL;
    score_max = 0;
    fmt = first_oformat;
    while (fmt != NULL) {
        score = 0;
        if (fmt->name && short_name && !strcmp(fmt->name, short_name))
            score += 100;
        if (fmt->mime_type && mime_type && !strcmp(fmt->mime_type, mime_type))
            score += 10;
        if (filename && fmt->extensions &&
            match_ext(filename, fmt->extensions)) {
            score += 5;
        }
        if (score > score_max) {
            score_max = score;
            fmt_found = fmt;
        }
        fmt = fmt->next;
    }
    return fmt_found;
}

AVOutputFormat *guess_stream_format(const char *short_name, const char *filename,
                             const char *mime_type)
{
    AVOutputFormat *fmt = guess_format(short_name, filename, mime_type);

    if (fmt) {
        AVOutputFormat *stream_fmt;
        char stream_format_name[64];

        snprintf(stream_format_name, sizeof(stream_format_name), "%s_stream", fmt->name);
        stream_fmt = guess_format(stream_format_name, NULL, NULL);

        if (stream_fmt)
            fmt = stream_fmt;
    }

    return fmt;
}

/**
 * Guesses the codec id based upon muxer and filename.
 */
enum CodecID av_guess_codec(AVOutputFormat *fmt, const char *short_name,
                            const char *filename, const char *mime_type, enum CodecType type){
    if(type == CODEC_TYPE_VIDEO){
        enum CodecID codec_id= CODEC_ID_NONE;

        if(!strcmp(fmt->name, "image2") || !strcmp(fmt->name, "image2pipe")){
            codec_id= av_guess_image2_codec(filename);
        }
        if(codec_id == CODEC_ID_NONE)
            codec_id= fmt->video_codec;
        return codec_id;
    }else if(type == CODEC_TYPE_AUDIO)
        return fmt->audio_codec;
    else
        return CODEC_ID_NONE;
}

/**
 * finds AVInputFormat based on input format's short name.
 */
AVInputFormat *av_find_input_format(const char *short_name)
{
    AVInputFormat *fmt;
    for(fmt = first_iformat; fmt != NULL; fmt = fmt->next) {
        if (!strcmp(fmt->name, short_name))
            return fmt;
    }
    return NULL;
}

/* memory handling */

/**
 * Default packet destructor.
 */
void av_destruct_packet(AVPacket *pkt)
{
    av_free(pkt->data);
    pkt->data = NULL; pkt->size = 0;
}

/**
 * Allocate the payload of a packet and intialized its fields to default values.
 *
 * @param pkt packet
 * @param size wanted payload size
 * @return 0 if OK. AVERROR_xxx otherwise.
 */
int av_new_packet(AVPacket *pkt, int size)
{
    void *data;
    if((unsigned)size > (unsigned)size + FF_INPUT_BUFFER_PADDING_SIZE)
        return AVERROR_NOMEM;
    data = av_malloc(size + FF_INPUT_BUFFER_PADDING_SIZE);
    if (!data)
        return AVERROR_NOMEM;
    memset(data + size, 0, FF_INPUT_BUFFER_PADDING_SIZE);

    av_init_packet(pkt);
    pkt->data = data;
    pkt->size = size;
    pkt->destruct = av_destruct_packet;
    return 0;
}

/**
 * Allocate and read the payload of a packet and intialized its fields to default values.
 *
 * @param pkt packet
 * @param size wanted payload size
 * @return >0 (read size) if OK. AVERROR_xxx otherwise.
 */
int av_get_packet(ByteIOContext *s, AVPacket *pkt, int size)
{
    int ret= av_new_packet(pkt, size);

    if(ret<0)
        return ret;

    pkt->pos= url_ftell(s);

    ret= get_buffer(s, pkt->data, size);
    if(ret<=0)
        av_free_packet(pkt);
    else
        pkt->size= ret;

    return ret;
}

/* This is a hack - the packet memory allocation stuff is broken. The
   packet is allocated if it was not really allocated */
int av_dup_packet(AVPacket *pkt)
{
    if (pkt->destruct != av_destruct_packet) {
        uint8_t *data;
        /* we duplicate the packet and don't forget to put the padding
           again */
        if((unsigned)pkt->size > (unsigned)pkt->size + FF_INPUT_BUFFER_PADDING_SIZE)
            return AVERROR_NOMEM;
        data = av_malloc(pkt->size + FF_INPUT_BUFFER_PADDING_SIZE);
        if (!data) {
            return AVERROR_NOMEM;
        }
        memcpy(data, pkt->data, pkt->size);
        memset(data + pkt->size, 0, FF_INPUT_BUFFER_PADDING_SIZE);
        pkt->data = data;
        pkt->destruct = av_destruct_packet;
    }
    return 0;
}

/* fifo handling */

int fifo_init(FifoBuffer *f, int size)
{
    f->buffer = av_malloc(size);
    if (!f->buffer)
        return -1;
    f->end = f->buffer + size;
    f->wptr = f->rptr = f->buffer;
    return 0;
}

void fifo_free(FifoBuffer *f)
{
    av_free(f->buffer);
}

int fifo_size(FifoBuffer *f, uint8_t *rptr)
{
    int size;

    if(!rptr)
        rptr= f->rptr;

    if (f->wptr >= rptr) {
        size = f->wptr - rptr;
    } else {
        size = (f->end - rptr) + (f->wptr - f->buffer);
    }
    return size;
}

/**
 * Get data from the fifo (returns -1 if not enough data).
 */
int fifo_read(FifoBuffer *f, uint8_t *buf, int buf_size, uint8_t **rptr_ptr)
{
    uint8_t *rptr;
    int size, len;

    if(!rptr_ptr)
        rptr_ptr= &f->rptr;
    rptr = *rptr_ptr;

    if (f->wptr >= rptr) {
        size = f->wptr - rptr;
    } else {
        size = (f->end - rptr) + (f->wptr - f->buffer);
    }

    if (size < buf_size)
        return -1;
    while (buf_size > 0) {
        len = f->end - rptr;
        if (len > buf_size)
            len = buf_size;
        memcpy(buf, rptr, len);
        buf += len;
        rptr += len;
        if (rptr >= f->end)
            rptr = f->buffer;
        buf_size -= len;
    }
    *rptr_ptr = rptr;
    return 0;
}

/**
 * Resizes a FIFO.
 */
void fifo_realloc(FifoBuffer *f, unsigned int new_size){
    unsigned int old_size= f->end - f->buffer;

    if(old_size < new_size){
        uint8_t *old= f->buffer;

        f->buffer= av_realloc(f->buffer, new_size);

        f->rptr += f->buffer - old;
        f->wptr += f->buffer - old;

        if(f->wptr < f->rptr){
            memmove(f->rptr + new_size - old_size, f->rptr, f->buffer + old_size - f->rptr);
            f->rptr += new_size - old_size;
        }
        f->end= f->buffer + new_size;
    }
}

void fifo_write(FifoBuffer *f, uint8_t *buf, int size, uint8_t **wptr_ptr)
{
    int len;
    uint8_t *wptr;

    if(!wptr_ptr)
        wptr_ptr= &f->wptr;
    wptr = *wptr_ptr;

    while (size > 0) {
        len = f->end - wptr;
        if (len > size)
            len = size;
        memcpy(wptr, buf, len);
        wptr += len;
        if (wptr >= f->end)
            wptr = f->buffer;
        buf += len;
        size -= len;
    }
    *wptr_ptr = wptr;
}

/* get data from the fifo (return -1 if not enough data) */
int put_fifo(ByteIOContext *pb, FifoBuffer *f, int buf_size, uint8_t **rptr_ptr)
{
    uint8_t *rptr = *rptr_ptr;
    int size, len;

    if (f->wptr >= rptr) {
        size = f->wptr - rptr;
    } else {
        size = (f->end - rptr) + (f->wptr - f->buffer);
    }

    if (size < buf_size)
        return -1;
    while (buf_size > 0) {
        len = f->end - rptr;
        if (len > buf_size)
            len = buf_size;
        put_buffer(pb, rptr, len);
        rptr += len;
        if (rptr >= f->end)
            rptr = f->buffer;
        buf_size -= len;
    }
    *rptr_ptr = rptr;
    return 0;
}

int filename_number_test(const char *filename)
{
    char buf[1024];
    if(!filename)
        return -1;
    return get_frame_filename(buf, sizeof(buf), filename, 1);
}

/**
 * Guess file format.
 */
AVInputFormat *av_probe_input_format(AVProbeData *pd, int is_opened)
{
    AVInputFormat *fmt1, *fmt;
    int score, score_max;

    fmt = NULL;
    score_max = 0;
    for(fmt1 = first_iformat; fmt1 != NULL; fmt1 = fmt1->next) {
        if (!is_opened && !(fmt1->flags & AVFMT_NOFILE))
            continue;
        score = 0;
        if (fmt1->read_probe) {
            score = fmt1->read_probe(pd);
        } else if (fmt1->extensions) {
            if (match_ext(pd->filename, fmt1->extensions)) {
                score = 50;
            }
        }
        if (score > score_max) {
            score_max = score;
            fmt = fmt1;
        }
    }
    return fmt;
}

/************************************************************/
/* input media file */