SDL播放声音

extern "C"
{
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libswscale/swscale.h>
#include <libswresample/swresample.h>
#include <libavutil/avstring.h>
#include <libavutil/pixfmt.h>
#include <libavutil/log.h>
};

#include <stdio.h>
#include <math.h>
#include <SDL.h>
#include <SDL_thread.h>


#pragma comment(lib, "libmingwex.lib")
#pragma comment(lib, "libgcc.lib")
#pragma comment(lib, "avformat.lib")
#pragma comment(lib, "avutil.lib")
#pragma comment(lib, "avcodec.lib")
#pragma comment(lib, "swresample.lib")

#pragma comment(lib, "SDL.lib")
#pragma comment(lib, "SDLmain.lib")

#define SDL_AUDIO_BUFFER_SIZE 1024 
#define MAX_AUDIOQ_SIZE (1 * 1024 * 1024)
#define FF_ALLOC_EVENT   (SDL_USEREVENT)
#define FF_REFRESH_EVENT (SDL_USEREVENT + 1)
#define FF_QUIT_EVENT (SDL_USEREVENT + 2)

typedef struct PacketQueue {//Queue
    AVPacketList *first_pkt, *last_pkt;
    int nb_packets;
    int size;
    SDL_mutex *mutex;
    SDL_cond *cond;
} PacketQueue;

typedef struct VideoState {//State
    char            filename[1024];
    AVFormatContext *ic;
    AVCodecContext *pCodecCtx;
	AVCodec        *pCodec;
    int             videoStream, audioStream;
    AVStream        *audio_st;
    AVFrame         *audio_frame;
    PacketQueue     audioq;
    unsigned int    audio_buf_size;
    unsigned int    audio_buf_index;
    AVPacket        audio_pkt;
    uint8_t         *audio_pkt_data;
    int             audio_pkt_size;
    uint8_t         *audio_buf;
    uint8_t         *audio_buf1;
    DECLARE_ALIGNED(16,uint8_t,audio_buf2)[AVCODEC_MAX_AUDIO_FRAME_SIZE * 4];
    enum AVSampleFormat  audio_src_fmt;
    enum AVSampleFormat  audio_tgt_fmt;
    int             audio_src_channels;
    int             audio_tgt_channels;
    int64_t         audio_src_channel_layout;
    int64_t         audio_tgt_channel_layout;
    int             audio_src_freq;
    int             audio_tgt_freq;
    struct SwrContext *swr_ctx;
    SDL_Thread      *parse_tid;//thread id
    int             quit;//flag 
} VideoState;

VideoState *global_video_state;//global state

void packet_queue_init(PacketQueue *q) {//init  queue
    memset(q, 0, sizeof(PacketQueue));
    q->mutex = SDL_CreateMutex();
    q->cond = SDL_CreateCond();
}

int packet_queue_put(PacketQueue *q, AVPacket *pkt) {//put pkt to pktQueue
    AVPacketList *pkt1;

    pkt1 = (AVPacketList *)av_malloc(sizeof(AVPacketList));
    if (!pkt1) {
        return -1;
    }
    pkt1->pkt = *pkt;//put pkt to PacketList 
    pkt1->next = NULL;

    SDL_LockMutex(q->mutex);

    if (!q->last_pkt) {//last_pkt = NULL, Queue element is  PacketList,we can not use packet directly
        q->first_pkt = pkt1;
    } else {//not first time
        q->last_pkt->next = pkt1;
    }

    q->last_pkt = pkt1;//update
    q->nb_packets++;//record nb_packet
    q->size += pkt1->pkt.size;//update pkt size in queue
    SDL_CondSignal(q->cond);
    SDL_UnlockMutex(q->mutex);
    return 0;
}

static int packet_queue_get(PacketQueue *q, AVPacket *pkt, int block) {//get data from queue
    AVPacketList *pkt1;
    int ret;

    SDL_LockMutex(q->mutex);//lock

    for(;;) {
        if(global_video_state->quit) {//is or not quit firstly
            ret = -1;
            break;
        }//quit，跳出循环

        pkt1 = q->first_pkt;//queue: first in, first out
        if (pkt1) {       
            q->first_pkt = pkt1->next;
            if (!q->first_pkt) {//if queue is over
                q->last_pkt = NULL;
            }
            q->nb_packets--;
            q->size -= pkt1->pkt.size;
            *pkt = pkt1->pkt;

            av_free(pkt1);
            ret = 1;//
            break;
        } else if (!block) {
            ret = 0;
            break;
        } else {
            SDL_CondWait(q->cond, q->mutex);//until data enough 
        }
    }
    SDL_UnlockMutex(q->mutex);
    return ret;
}

static void packet_queue_flush(PacketQueue *q) {//flush queue
    AVPacketList *pkt, *pkt1;

    SDL_LockMutex(q->mutex);//lock
    for (pkt = q->first_pkt; pkt != NULL; pkt = pkt1) {
        pkt1 = pkt->next;
        av_free_packet(&pkt->pkt);
        av_freep(&pkt);
    }
    q->last_pkt = NULL;
    q->first_pkt = NULL;
    q->nb_packets = 0;
    q->size = 0;
    SDL_UnlockMutex(q->mutex);//unlock
}

int audio_decode_frame(VideoState *is) {//core code   decoded information is saved in videostate-is
    int len1, len2, decoded_data_size;
    AVPacket *pkt = &is->audio_pkt;
    int got_frame = 0;
    int64_t dec_channel_layout;
    int wanted_nb_samples, resampled_data_size;

    for (;;) {//dead loop
        while (is->audio_pkt_size > 0) {
            if (!is->audio_frame) {
                if (!(is->audio_frame = avcodec_alloc_frame())) {
                    return AVERROR(ENOMEM);           
                }
            } else 
                avcodec_get_frame_defaults(is->audio_frame);//AVFrame should be set to default values
            len1 = avcodec_decode_audio4(is->audio_st->codec, is->audio_frame, &got_frame,  pkt);
            if (len1 < 0) {
                // error, skip the frame
                is->audio_pkt_size = 0;
                break;
            }

            is->audio_pkt_data += len1;
            is->audio_pkt_size -= len1;

            if (!got_frame) 
                continue;
                              
           /* decoded_data_size = av_samples_get_buffer_size(NULL,
                                is->audio_frame->channels,							 
                               is->audio_frame->nb_samples,
                                is->audio_frame->format, 1);*/
			decoded_data_size = av_samples_get_buffer_size(NULL,
				is->pCodecCtx->channels,
				is->audio_frame->nb_samples,
				AVSampleFormat(is->audio_frame->format), 1);//get decoded_data_size

          /*  dec_channel_layout = (is->audio_frame->channel_layout && is->audio_frame->channels
                                  == av_get_channel_layout_nb_channels(is->audio_frame->channel_layout))
                                 ? is->audio_frame->channel_layout
                                 : av_get_default_channel_layout(is->audio_frame->channels);*/

			dec_channel_layout = (is->pCodecCtx->channel_layout && is->pCodecCtx->channels
				== av_get_channel_layout_nb_channels(is->pCodecCtx->channel_layout))
				? is->pCodecCtx->channel_layout
				: av_get_default_channel_layout(is->pCodecCtx->channels);

            wanted_nb_samples =  is->audio_frame->nb_samples;

            //fprintf(stderr, "wanted_nb_samples = %d
", wanted_nb_samples);
            //解码出来的音频与原先设定的格式不一致,则重采样
            if (is->audio_frame->format != is->audio_src_fmt ||
                dec_channel_layout != is->audio_src_channel_layout ||
                is->pCodecCtx->sample_rate != is->audio_src_freq ||
                (wanted_nb_samples != is->audio_frame->nb_samples && !is->swr_ctx)) {
                if (is->swr_ctx) swr_free(&is->swr_ctx);
                is->swr_ctx = swr_alloc_set_opts(NULL, //get swr_ctx
                                                 is->audio_tgt_channel_layout,
                                                 is->audio_tgt_fmt,
                                                 is->audio_tgt_freq,
                                                 dec_channel_layout,
                                                 AVSampleFormat(is->audio_frame->format),
                                                 is->pCodecCtx->sample_rate,
                                                 0, NULL);
                if (!is->swr_ctx || swr_init(is->swr_ctx) < 0) {//init
                    fprintf(stderr, "swr_init() failed
");
                    break;
                }//get src parameters
                is->audio_src_channel_layout = dec_channel_layout;
                is->audio_src_channels = is->audio_st->codec->channels;
                is->audio_src_freq = is->audio_st->codec->sample_rate;
                is->audio_src_fmt = is->audio_st->codec->sample_fmt;
            }
            if (is->swr_ctx) {  
               // const uint8_t *in[] = { is->audio_frame->data[0] };
                const uint8_t **in = (const uint8_t **)is->audio_frame->extended_data; 
                uint8_t *out[] = { is->audio_buf2 };
				if (wanted_nb_samples != is->audio_frame->nb_samples) {//compensate samples
					 swr_compensate(is->swr_ctx, (wanted_nb_samples - is->audio_frame->nb_samples)
												 * is->audio_tgt_freq / is->pCodecCtx->sample_rate,
												 wanted_nb_samples * is->audio_tgt_freq / is->pCodecCtx->sample_rate);
				 }
                 
                len2 = swr_convert(is->swr_ctx, out,// in data is changed by swr_ctx
                                   sizeof(is->audio_buf2)
                                   / is->audio_tgt_channels
                                   / av_get_bytes_per_sample(is->audio_tgt_fmt),//tgt_nb_samples
                                   in, is->audio_frame->nb_samples);//convert
                if (len2 < 0) {
                    fprintf(stderr, "swr_convert() failed
");
                    break;
                }
                if (len2 == sizeof(is->audio_buf2) / is->audio_tgt_channels / av_get_bytes_per_sample(is->audio_tgt_fmt)) {
                    fprintf(stderr, "warning: audio buffer is probably too small
");
                    swr_init(is->swr_ctx);
                }
                is->audio_buf = is->audio_buf2;//audio_buff
                resampled_data_size = len2 * is->audio_tgt_channels * av_get_bytes_per_sample(is->audio_tgt_fmt);//resampled_data_size
            } else {
				resampled_data_size = decoded_data_size;//not resampled
                is->audio_buf = is->audio_frame->data[0];      
            }
            // We have data, return it and come back for more later
            return resampled_data_size;  //返回重采样后的长度
        }//decode one frame

        if (pkt->data) av_free_packet(pkt);
		memset(pkt, 0, sizeof(*pkt));
        if (is->quit) return -1;
        if (packet_queue_get(&is->audioq, pkt, 1) < 0) return -1;//get next packet

        is->audio_pkt_data = pkt->data;
        is->audio_pkt_size = pkt->size;
    }
}

void audio_callback(void *userdata, Uint8 *stream, int len) {
    VideoState *is = (VideoState *)userdata;
    int len1, audio_data_size;
	printf("audio callback 1 len=%d
",len);

    while (len > 0) {     
        if (is->audio_buf_index >= is->audio_buf_size) {
            audio_data_size = audio_decode_frame(is);//decode one frame,return size
            if(audio_data_size < 0) {
                /* silence */
                is->audio_buf_size = 1024;
                memset(is->audio_buf, 0, is->audio_buf_size);
            } else {
                is->audio_buf_size = audio_data_size;
            }
            is->audio_buf_index = 0;     
			printf("audio callback 2 (audio_buf_size,audio_buf_index) = (%d,%d)
",is->audio_buf_size,is->audio_buf_index);
        }
             
        len1 = is->audio_buf_size - is->audio_buf_index;
        if (len1 > len) {
            len1 = len;
        }
    
        memcpy(stream, (uint8_t *)is->audio_buf + is->audio_buf_index, len1); 
        len -= len1;
        stream += len1;
        is->audio_buf_index += len1;
        printf("audio callback 3 (len1,len,audio_buf_index) = (%d,%d,%d)
",len1,len,is->audio_buf_index); 
	}
}

int stream_component_open(VideoState *is, int stream_index) {//open stream 
    AVFormatContext *ic = is->ic;
    AVCodecContext *codecCtx;
    AVCodec *codec;
    SDL_AudioSpec wanted_spec, spec;
    int64_t wanted_channel_layout = 0;
    int wanted_nb_channels;
	const int next_nb_channels[] = {0, 0, 1 ,6, 2, 6, 4, 6};

    if (stream_index < 0 || stream_index >= ic->nb_streams) {
        return -1;
    }
	
    codecCtx = ic->streams[stream_index]->codec;
	is->pCodecCtx=codecCtx;//Add
	wanted_nb_channels = codecCtx->channels;//wanted parameters
	if(!wanted_channel_layout || wanted_nb_channels != av_get_channel_layout_nb_channels(wanted_channel_layout)) {
		wanted_channel_layout = av_get_default_channel_layout(wanted_nb_channels);
		wanted_channel_layout &= ~AV_CH_LAYOUT_STEREO_DOWNMIX;
	}
	
	wanted_spec.channels = av_get_channel_layout_nb_channels(wanted_channel_layout);
	wanted_spec.freq = codecCtx->sample_rate;
	if (wanted_spec.freq <= 0 || wanted_spec.channels <= 0) {
		fprintf(stderr, "Invalid sample rate or channel count!
");
		return -1;
	}
	wanted_spec.format = AUDIO_S16SYS;
	wanted_spec.silence = 0;
	wanted_spec.samples = SDL_AUDIO_BUFFER_SIZE;
	wanted_spec.callback = audio_callback;//callback
	wanted_spec.userdata = is;
	
	while(SDL_OpenAudio(&wanted_spec, &spec) < 0) {//OpenAudio
		fprintf(stderr, "SDL_OpenAudio (%d channels): %s
", wanted_spec.channels, SDL_GetError());
		wanted_spec.channels = next_nb_channels[FFMIN(7, wanted_spec.channels)];
		if(!wanted_spec.channels) {
			fprintf(stderr, "No more channel combinations to tyu, audio open failed
");
			return -1;
		}
		wanted_channel_layout = av_get_default_channel_layout(wanted_spec.channels);
	}

	if (spec.format != AUDIO_S16SYS) {
		fprintf(stderr, "SDL advised audio format %d is not supported!
", spec.format);
		return -1;
	}
	if (spec.channels != wanted_spec.channels) {
		wanted_channel_layout = av_get_default_channel_layout(spec.channels);
		if (!wanted_channel_layout) {
			fprintf(stderr, "SDL advised channel count %d is not supported!
", spec.channels);
			return -1;
		}
	}

	fprintf(stderr, "%d: wanted_spec.format = %d
", __LINE__, wanted_spec.format);
	fprintf(stderr, "%d: wanted_spec.samples = %d
", __LINE__, wanted_spec.samples);
	fprintf(stderr, "%d: wanted_spec.channels = %d
", __LINE__, wanted_spec.channels);
	fprintf(stderr, "%d: wanted_spec.freq = %d
", __LINE__, wanted_spec.freq);

	fprintf(stderr, "%d: spec.format = %d
", __LINE__, spec.format);
	fprintf(stderr, "%d: spec.samples = %d
", __LINE__, spec.samples);
	fprintf(stderr, "%d: spec.channels = %d
", __LINE__, spec.channels);
	fprintf(stderr, "%d: spec.freq = %d
", __LINE__, spec.freq);
    
	is->audio_src_fmt = is->audio_tgt_fmt = AV_SAMPLE_FMT_S16;//src parameters
	is->audio_src_freq = is->audio_tgt_freq = spec.freq;
	is->audio_src_channel_layout = is->audio_tgt_channel_layout = wanted_channel_layout;
	is->audio_src_channels = is->audio_tgt_channels = spec.channels;
    
    codec = avcodec_find_decoder(codecCtx->codec_id);//find decoder
	is->pCodec=codec;//Add
    if (!codec || (avcodec_open2(codecCtx, codec, NULL) < 0)) {//Unsupported codec
        fprintf(stderr, "Unsupported codec!
");
        return -1;
    }
	ic->streams[stream_index]->discard = AVDISCARD_DEFAULT;
    switch(codecCtx->codec_type) {
    case AVMEDIA_TYPE_AUDIO:
        is->audioStream = stream_index;
        is->audio_st = ic->streams[stream_index];
        is->audio_buf_size = 0;
        is->audio_buf_index = 0;
        memset(&is->audio_pkt, 0, sizeof(is->audio_pkt));
        packet_queue_init(&is->audioq);
        SDL_PauseAudio(0);
        break;
    default:
        break;
    }
}
/*
static void stream_component_close(VideoState *is, int stream_index) {
	AVFormatContext *oc = is->;
	AVCodecContext *avctx;

	if(stream_index < 0 || stream_index >= ic->nb_streams)	return;
	avctx = ic->streams[stream_index]->codec;

}
*/
static int decode_thread(void *arg) {
	//初始化参数，函数内部处理得到的相关参数赋给 is
    VideoState *is = (VideoState *)arg;
    AVFormatContext *ic = NULL;
    AVPacket pkt1, *packet = &pkt1;
    int ret, i, audio_index = -1;

    is->audioStream=-1;
    global_video_state = is;//全局状态
    if (avformat_open_input(&ic, is->filename, NULL, NULL) != 0) {
        return -1;
    }
    is->ic = ic;
    if (avformat_find_stream_info(ic, NULL) < 0) {//打开流信息
        return -1;
    }
    av_dump_format(ic, 0, is->filename, 0);
    for (i=0; i<ic->nb_streams; i++) {
        if (ic->streams[i]->codec->codec_type==AVMEDIA_TYPE_AUDIO && audio_index < 0) {//打开第一条音频流
            audio_index=i;
            break;
        }
    }
    if (audio_index >= 0) {
        stream_component_open(is, audio_index);//打开音频流
    }
    if (is->audioStream < 0) {
        fprintf(stderr, "%s: could not open codecs
", is->filename);
        goto fail;
    }
    // main decode loop
    for(;;) {
        if(is->quit) break;
        if (is->audioq.size > MAX_AUDIOQ_SIZE) {
            SDL_Delay(10);//so fast
            continue;
        }
        ret = av_read_frame(is->ic, packet);//read data to one packet
        if (ret < 0) {
            if(ret == AVERROR_EOF || url_feof(is->ic->pb)) {//error or end
                break;
            }
            if(is->ic->pb && is->ic->pb->error) {
                break;
            }
            continue;
        }

        if (packet->stream_index == is->audioStream) {//packet data to audioq   
            packet_queue_put(&is->audioq, packet);
        } else {
            av_free_packet(packet);
        }
    }

    while (!is->quit) {// delay
        SDL_Delay(100); 
    }

fail: {//if  fail
        SDL_Event event;
        event.type = FF_QUIT_EVENT;
        event.user.data1 = is;
        SDL_PushEvent(&event);
    }

    return 0;
}

int main(int argc, char *argv[])
{
    SDL_Event       event;
    VideoState      *is;

    is = (VideoState *)av_mallocz(sizeof(VideoState));

    //if (argc < 2) {
    //    fprintf(stderr, "Usage: test <file>
");
    //    exit(1);
    //}

    argv[1]="test.mp4";
    av_register_all();//注册编解码库

    if (SDL_Init(SDL_INIT_AUDIO)) { //初始化音频SDL
        fprintf(stderr, "Could not initialize SDL - %s
", SDL_GetError());
        exit(1);
    }
        
    av_strlcpy(is->filename,argv[1], sizeof(is->filename));

    is->parse_tid = SDL_CreateThread(decode_thread, is);
    if (!is->parse_tid) {
        av_free(is);
        return -1;
    }

    for(;;) {
        SDL_WaitEvent(&event);
        switch(event.type) {
        case FF_QUIT_EVENT:
        case SDL_QUIT://退出
            is->quit = 1;
            SDL_Quit();
            exit(0);
            break;
        default:
            break;
        }
    }
    return 0;
}