知识总结

来源：互联网发布：新浪视频mac客户端编辑：程序博客网时间：2024/04/28 08:54

(1)av_rescale_q(int a,R b,R q) 等价 a * b * (1/q)

(2)mp3 spf = 576: 1152

(3)url_fseek()

{

s->seek();

s->buf_ptr = s->buffer; //当前地址指向缓冲区开始处

}

get_buffer

{

            if(size > s->buffer_size && !s->update_checksum)            //需要的数据量大于缓冲区大小就直接从源读取
           {
                if(s->read_packet)
                    len = s->read_packet(s->opaque, buf, size);
                if (len <= 0)
               {
                    /* do not modify buffer if EOF reached so that a seek back can
                    be done without rereading data */
                    s->eof_reached = 1;
                    if(len<0)
                        s->error= len;
                    break;
                }
               else
               {
                    s->pos += len;
                    size -= len;
                    buf += len;
                    s->buf_ptr = s->buffer;                              //当前地址和结尾地址都指向缓冲区开始处
                    s->buf_end = s->buffer/* + len*/;
                }
            }

}

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