使用ffmpeg为库编写的小型多媒体播放器源代码

今天突发奇想，就在以前音频播放器（详细情况请看这里——http://blog.csdn.net/baymoon/archive/2006/11/16/1388693.aspx）的基础上用ffmpeg写了个简单的多媒体播放器，这里把源代码贴出来，供大家参评；这里的多媒体播放，并没有用到什么很强大的音视频同步技术，而只是简单的使用了视频随着音频同步，想必你看了代码之后会有所悟的。。。不多说了，看代码。。。

/**//***************************************************************************
 *            main.cc
 *
 *  Thu Nov  9 20:47:33 2006
 *  Copyright  2006
 *  Email lsosa.cs2c
 ****************************************************************************/
#include <avcodec.h>
#include <avformat.h>
#include <avutil.h>
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <X11/Xlib.h>
#include <sys/soundcard.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sched.h>
#include <SDL/SDL.h>

#define ALL_DEBUG

#ifdef ALL_DEBUG
    #define AV_DEBUG
    #define AUDIO_DEBUG
#endif

//------------------------------------------------------------------------------
// manipulations for file
int open_file (char *file_name, int mode)
{
    // open file file_name and return the file descriptor;
    int fd;

    if ((fd = open (file_name, mode)) < 0)
    {
        fprintf (stderr, " Can't open %s! ", file_name);
        exit (-1);
    }
    return fd;
}

int set_audio (int fd, AVCodecContext * pCodecCtx)
{
    // set the properties of audio device with pCodecCtx;

    int i, err;
    /**//* 设置适当的参数，使得声音设备工作正常 */
    /**//* 详细情况请参考Linux关于声卡编程的文档 */

    i = 0;
    ioctl (fd, SNDCTL_DSP_RESET, &i);
    i = 0;
    ioctl (fd, SNDCTL_DSP_SYNC, &i);
    i = 1;
    ioctl (fd, SNDCTL_DSP_NONBLOCK, &i);

    // set sample rate;
    #ifdef AUDIO_DEBUG
    printf ("pCodecCtx->sample_rate:%d ", pCodecCtx->sample_rate);
    #endif
    i = pCodecCtx->sample_rate;
    if (ioctl (fd, SNDCTL_DSP_SPEED, &i) == -1)
    {
        fprintf (stderr, "Set speed to %d failed:%s ", i,
             strerror (errno));
        return (-1);
    }
    if (i != pCodecCtx->sample_rate)
    {
        fprintf (stderr, "do not support speed %d,supported is %d ",
             pCodecCtx->sample_rate, i);
        return (-1);
    }

    // set channels;
    i = pCodecCtx->channels;
    #ifdef AUDIO_DEBUG
    printf ("pCodecCtx->channels:%d ", pCodecCtx->channels);
    #endif
    if ((ioctl (fd, SNDCTL_DSP_CHANNELS, &i)) == -1)
    {
        fprintf (stderr, "Set Audio Channels %d failed:%s ", i,
             strerror (errno));
        return (-1);
    }
    if (i != pCodecCtx->channels)
    {
        fprintf (stderr, "do not support channel %d,supported %d ",
            pCodecCtx->channels, i);
        return (-1);
    }
    // set bit format;
    i = AFMT_S16_LE;
    if (ioctl (fd, SNDCTL_DSP_SETFMT, &i) == -1)
    {
        fprintf (stderr, "Set fmt to bit %d failed:%s ", i,
             strerror (errno));
        return (-1);
    }
    if (i != AFMT_S16_LE)
    {
        fprintf (stderr, "do not support bit %d, supported %d ",
             AFMT_S16_LE, i);
        return (-1);
    }

    // set application buffer size;
    // i = (0x00032 << 16) + 0x000c;        // 32 4kb buffer;
    // ioctl (fd, SNDCTL_DSP_SETFRAGMENT, &i);
    i = 1;
    ioctl (fd, SNDCTL_DSP_PROFILE, &i);

    return 0;
}

void close_file (int fd)
{
    // close the file pointed by file descriptor fd;
    close (fd);
}

//------------------------------------------------------------------------------
// handle audio;

void display_AVCodecContext(AVCodecContext *pCodecCtx){
    //
    #define STDOUT stderr
    fprintf(STDOUT, "pCodecCtx->bit_rate:%d ", pCodecCtx->bit_rate);
    fprintf(STDOUT, "pCodecCtx->sample_rate:%d ", pCodecCtx->sample_rate);
    fprintf(STDOUT, "pCodecCtx->channels:%d ", pCodecCtx->channels);
    fprintf(STDOUT, "pCodecCtx->frame_size:%d ", pCodecCtx->frame_size);
    fprintf(STDOUT, "pCodecCtx->frame_number:%d ", pCodecCtx->frame_number);
    fprintf(STDOUT, "pCodecCtx->delay:%d ", pCodecCtx->delay);
    fprintf(STDOUT, "pCodecCtx->frame_bits:%d ", pCodecCtx->frame_bits);
}

// error if return -1;
// success if return 0;
// 这里要用到指向指针的指针，否则传不到值；
int av_init (char *file_name, AVFormatContext ** pFormatCtx,
    AVCodecContext ** pAudioCodecCtx, int *p_audioStream,
    AVCodecContext ** pVideoCodecCtx, int *p_videoStream)
{
    // init the codec and format of input file file_name;
    int audioStream, i;
    int videoStream;
    AVCodec *pAudioCodec;
    AVCodec *pVideoCodec;
    // catch error
    assert(file_name != NULL);
    assert(*pFormatCtx != NULL);
    assert(*pAudioCodecCtx != NULL);

    // Register all formats and codecs
    av_register_all ();

    // open file
    if (av_open_input_file (pFormatCtx, file_name, NULL, 0, NULL) != 0){
        // Couldn't open file
        fprintf (stderr, " Can't open %s! ", file_name);
        return -1;
    }

    // Retrieve stream information
    if (av_find_stream_info (*pFormatCtx) < 0){
        // Couldn't find stream information
        return -1;
    }

    #ifdef AV_DEBUG
    // Dump information about file onto standard error
    dump_format (*pFormatCtx, 0, file_name, false);
    #endif

    // Find the first audio and video stream respectively
    audioStream = -1;
    videoStream = -1;
    for (i = 0; i < (*pFormatCtx)->nb_streams; i++){
        if ((*pFormatCtx)->streams[i]->codec->codec_type ==
            CODEC_TYPE_AUDIO)
        {
            audioStream = i;
        }else if ((*pFormatCtx)->streams[i]->codec->codec_type ==
            CODEC_TYPE_VIDEO){
            videoStream = i;
        }
    }

    #ifdef AV_DEBUG
    // dump_stream_info(pFormatCtx);
    #endif

    // exclude error
    if (audioStream == -1){
        // Didn't find a audio or video stream
        // return -1;
        printf("No Audio ");
    }
    if (videoStream == -1){
        // Didn't find a audio or video stream
        // return -1;
        printf("No Video ");
    }

    // Get a pointer to the codec context for the audio stream
    *pAudioCodecCtx = (*pFormatCtx)->streams[audioStream]->codec;
    *pVideoCodecCtx = (*pFormatCtx)->streams[videoStream]->codec;

    // Find the decoder for the audio stream
    pAudioCodec = avcodec_find_decoder ((*pAudioCodecCtx)->codec_id);
    pVideoCodec = avcodec_find_decoder ((*pVideoCodecCtx)->codec_id);
    //
    if (pAudioCodec == NULL){
        return -1;    // Codec not found
    }
    if (pVideoCodec == NULL){
        return -1;    // Codec not found
    }

    // Open audio codec
    if (avcodec_open ((*pAudioCodecCtx), pAudioCodec) < 0){
        return -1;    // Could not open codec
    }
    // Open video codec
    if (avcodec_open ((*pVideoCodecCtx), pVideoCodec) < 0){
        return -1;    // Could not open codec
    }

    #ifdef AUDIO_DEBUG
    // printf ("pCodecCtx->sample_rate:%d, audioStream:%d ", (*pCodecCtx)->sample_rate, audioStream);
    // display_AVCodecContext(*pCodecCtx);
    #endif

    *p_audioStream = audioStream;
    *p_videoStream = videoStream;

    return 0;
}

void av_play (AVFormatContext * pFormatCtx,
    AVCodecContext * pAudioCodecCtx, int audioStream,
    AVCodecContext * pVideoCodecCtx, int videoStream)
    // AVCodecContext * pCodecCtx, int audioStream)
{
    // which was read from one frame;
    AVPacket packet;
    uint32_t len;
    uint8_t decompressed_audio_buf[(AVCODEC_MAX_AUDIO_FRAME_SIZE * 3) / 2];
    int decompressed_audio_buf_size;
    uint8_t * p_decompressed_audio_buf;
    int fd = -1;    // audio file or test file?
    char filename[64] = "/dev/dsp";
    int mode = O_WRONLY;
    // Video;
    AVFrame *pFrame;
    AVFrame *pFrameYUV;
    int frameFinished;

    /**////////// SDL initialization
    SDL_Surface *screen =
    SDL_SetVideoMode (pVideoCodecCtx->width, pVideoCodecCtx->height, 0, SDL_HWSURFACE);
    SDL_Overlay *overlay =
    SDL_CreateYUVOverlay (pVideoCodecCtx->width, pVideoCodecCtx->height,
              SDL_YV12_OVERLAY,
              screen);
    static SDL_Rect rect;
    rect.x = 0;
    rect.y = 0;
    rect.w = pVideoCodecCtx->width;
    rect.h = pVideoCodecCtx->height;
    /**///////////

    // open audio file or written file
    // printf("fd:%d", fd);
    fd = open_file(filename, mode);
    // printf("fd:%d", fd);
    //
    set_audio(fd, pAudioCodecCtx);

    //
    printf("(AVCODEC_MAX_AUDIO_FRAME_SIZE * 3) / 2=%d ", (AVCODEC_MAX_AUDIO_FRAME_SIZE * 3) / 2);
    printf("AVCODEC_MAX_AUDIO_FRAME_SIZE=%d ", AVCODEC_MAX_AUDIO_FRAME_SIZE);

    // for a test
    // char test_file[256] = "my_pcm.pcm";
    // fd = open_file(test_file, mode);

    #ifdef AV_DEBUG
    static int size = 0;
    #endif
    //

    // set the sched priority
    // 这是为了提高音频优先级；不晓得起作用没；
    int policy = SCHED_FIFO;
    sched_setscheduler(0, policy, NULL);

    // Allocate video frame
    pFrame = avcodec_alloc_frame ();
    // Allocate an AVFrame structure
    pFrameYUV = avcodec_alloc_frame ();
    if (pFrameYUV == NULL)
        return;

    // Set SDL events
    SDL_EventState (SDL_ACTIVEEVENT, SDL_IGNORE);
    SDL_EventState (SDL_MOUSEMOTION, SDL_IGNORE);
    // SDL_ShowCursor (SDL_ENABLE);

    int write_buf_size = 4196;
    int written_size;
    while ((av_read_frame (pFormatCtx, &packet) >= 0)
        && (SDL_PollEvent (NULL) == 0))
    {
        // Is this a packet from the audio stream?
        // 判断是否音频帧；
        if (packet.stream_index == audioStream)
        {
            // Decode audio frame
            // 解码音频数据为pcm数据；
            len = avcodec_decode_audio (pAudioCodecCtx,
                            (int16_t *)decompressed_audio_buf,
                            &decompressed_audio_buf_size,        // it is the decompressed frame in BYTES 解码后的数据大小，字节为单位；
                            packet.data,
                            packet.size );
            // printf("len:%d, packet.size:%d ", len, packet.size);
            // printf("packet.pts:%d packet.dts:%d ", packet.pts, packet.dts);
            if ( len < 0 ){
                // if error len = -1
                printf("+----- error in decoding audio frame ");
                // exit(0);
            }
            // audio_buf_info info;
            p_decompressed_audio_buf = decompressed_audio_buf;
            while ( decompressed_audio_buf_size > 0 ){
                // 解码后数据不为零，则播放之，为零，则；
                written_size = write(fd, p_decompressed_audio_buf, decompressed_audio_buf_size);
                if ( written_size == -1 ){
                    // printf("error:decompressed_audio_buf_size:%d, decompressed_audio_buf_size:%d, %s ",
                                decompressed_audio_buf_size, decompressed_audio_buf_size,strerror(errno));
                    // usleep(100);
                    continue;
                }
                // printf("decompressed_audio_buf_size:%d, written_size:%d ",
                            decompressed_audio_buf_size, written_size);
                decompressed_audio_buf_size -= written_size;
                p_decompressed_audio_buf += written_size;
            }// end while
        }
        else if (packet.stream_index == videoStream)
        {
            // Decode video frame
            avcodec_decode_video (pVideoCodecCtx, pFrame, &frameFinished,
                    packet.data, packet.size);
            // Did we get a video frame?
            if (frameFinished) {
            // Convert the image from its native format to YUV, and display

            SDL_LockYUVOverlay (overlay);
            pFrameYUV->data[0] = overlay->pixels[0];
            pFrameYUV->data[1] = overlay->pixels[2];
            pFrameYUV->data[2] = overlay->pixels[1];

            pFrameYUV->linesize[0] = overlay->pitches[0];
            pFrameYUV->linesize[1] = overlay->pitches[2];
            pFrameYUV->linesize[2] = overlay->pitches[1];

            img_convert ((AVPicture *) pFrameYUV, PIX_FMT_YUV420P,
                        (AVPicture *) pFrame, pVideoCodecCtx->pix_fmt,
                        pVideoCodecCtx->width, pVideoCodecCtx->height);
            SDL_UnlockYUVOverlay (overlay);
            SDL_DisplayYUVOverlay (overlay, &rect);
            /**////
            // SDL_Delay (33);
            }
        }// end if
        // Free the packet that was allocated by av_read_frame
        av_free_packet (&packet);
    }// end while of reading one frame;

    // Free the RGB image
    av_free (pFrameYUV);
    // Free the YUV frame
    av_free (pFrame);
    // for test lsosa
    // printf("size = %d ", size / 1024 / 1024 );
    SDL_FreeYUVOverlay (overlay);

    close_file(fd);
}

void av_close (AVFormatContext * pFormatCtx, AVCodecContext * pAudioCodecCtx,
    AVCodecContext * pVideoCodecCtx)
{
    // close the file and codec
    // Close the codec
    avcodec_close (pAudioCodecCtx);
    // Close the codec
    avcodec_close (pVideoCodecCtx);

    // Close the video file
    av_close_input_file (pFormatCtx);
}

//------------------------------------------------------------------------------

int main (int argc, char **argv){
    //
    AVFormatContext *pFormatCtx;
    int audioStream = -1;
    int videoStream = -1;
    AVCodecContext *pAudioCodecCtx;
    AVCodecContext *pVideoCodecCtx;

    // exclude the error about args;
    if ( argc != 2 ){
        printf("please give a file name ");
        exit(0);
    }

    // 注意：这里要用到指向指针的指针，是因为这个初始化函数需要对指针的地址进行改动，
    // 所以，只有这么做，才能达到目的；
    if ( av_init(argv[1], &pFormatCtx, &pAudioCodecCtx, &audioStream, &pVideoCodecCtx, &videoStream) < 0 ){
        //
        fprintf(stderr, "error when av_init ");
    }

    // play the audio file
    av_play(pFormatCtx, pAudioCodecCtx, audioStream, pVideoCodecCtx, videoStream);

    // close all the opend files
    av_close(pFormatCtx, pAudioCodecCtx, pVideoCodecCtx);

}