[原]如何在Android用FFmpeg+SDL2.0之同步视频

关于视频同步的原理可以参考http://dranger.com/ffmpeg/tutorial05.html 和 [原]基础学习视频解码之同步视频 这两篇文章，本文是在这两篇的基础上移植到了Android上面，并且修正了声音解码的问题。


因此，我们有三种选择：同步视频到音频，同步音频到视频，或者两者同步至一个外部时钟（如计算机）。现在，我们将同步视频到音频。

/*
* SDL_Lesson.c
*
*  Created on: Aug 12, 2014
*      Author: clarck
*/
#include <jni.h>
#include <android/native_window_jni.h>
#include "SDL.h"
#include "SDL_thread.h"
#include "SDL_events.h"
#include "../include/logger.h"
#include "../ffmpeg/include/libavcodec/avcodec.h"
#include "../ffmpeg/include/libavformat/avformat.h"
#include "../ffmpeg/include/libavutil/pixfmt.h"
#include "../ffmpeg/include/libswscale/swscale.h"
#include "../ffmpeg/include/libswresample/swresample.h"

#define SDL_AUDIO_BUFFER_SIZE 1024

#define MAX_AUDIO_SIZE (5 * 16 * 1024)
#define MAX_VIDEO_SIZE (5 * 256 * 1024)

#define AV_SYNC_THRESHOLD 0.01
#define AV_NOSYNC_THRESHOLD 10.0

#define FF_ALLOC_EVENT (SDL_USEREVENT)
#define FF_REFRESH_EVENT (SDL_USEREVENT + 1)
#define FF_QUIT_EVENT    (SDL_USEREVENT + 2)

#define VIDEO_PICTURE_QUEUE_SIZE 1
#define AVCODEC_MAX_AUDIO_FRAME_SIZE 192000 // 1 second of 48khz 32bit audio

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

typedef struct VideoPicture {
SDL_Window *screen;
SDL_Renderer *renderer;
SDL_Texture *bmp;

AVFrame* rawdata;
int width, height; /*source height & width*/
int allocated;
double pts;
} VideoPicture;

typedef struct VideoState {
char filename[1024];
AVFormatContext *ic;
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;
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;

AVStream *video_st;
PacketQueue videoq;

VideoPicture pictq[VIDEO_PICTURE_QUEUE_SIZE];
int pictq_size, pictq_rindex, pictq_windex;
SDL_mutex *pictq_mutex;
SDL_cond *pictq_cond;

SDL_Thread *parse_tid;
SDL_Thread *audio_tid;
SDL_Thread *video_tid;

AVIOContext *io_ctx;
struct SwsContext *sws_ctx;

double audio_clock;
int audio_hw_buf_size;
double frame_timer;
double frame_last_pts;
double frame_last_delay;
double video_clock; ///<pts of last decoded frame / predicted pts of next decoded frame

int quit;
} VideoState;

VideoState *global_video_state;

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

int packet_queue_put(PacketQueue *q, AVPacket *pkt) {
AVPacketList *pkt1;

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

SDL_LockMutex(q->mutex);

if (!q->last_pkt) {
q->first_pkt = pkt1;
} else {
q->last_pkt->next = pkt1;
}

q->last_pkt = pkt1;
q->nb_packets++;
q->size += pkt1->pkt.size;
SDL_CondSignal(q->cond);
SDL_UnlockMutex(q->mutex);
return 0;
}

static int packet_queue_get(PacketQueue *q, AVPacket *pkt, int block) {
AVPacketList *pkt1;
int ret;

SDL_LockMutex(q->mutex);

for (;;) {
if (global_video_state->quit) {
ret = -1;
break;
}

pkt1 = q->first_pkt;
if (pkt1) {
q->first_pkt = pkt1->next;
if (!q->first_pkt) {
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);
}
}

SDL_UnlockMutex(q->mutex);

return ret;
}

double get_audio_clock(VideoState *is) {
double pts;
int hw_buf_size, bytes_per_sec, n;

pts = is->audio_clock; /* maintained in the audio thread */
hw_buf_size = is->audio_buf_size - is->audio_buf_index;
bytes_per_sec = 0;
n = is->audio_st->codec->channels * 2;
if (is->audio_st) {
bytes_per_sec = is->audio_st->codec->sample_rate * n;
}
if (bytes_per_sec) {
pts -= (double) hw_buf_size / bytes_per_sec;
}
return pts;
}

int audio_decode_frame(VideoState *is, double *pts_ptr) {
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, n;

double pts;

for (;;) {
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);

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;

/* 计算解码出来的桢需要的缓冲大小 */
decoded_data_size = av_samples_get_buffer_size(NULL,
is->audio_frame->channels, is->audio_frame->nb_samples,
is->audio_frame->format, 1);

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);

wanted_nb_samples = is->audio_frame->nb_samples;

if (is->audio_frame->format != is->audio_src_fmt
|| dec_channel_layout != is->audio_src_channel_layout
|| is->audio_frame->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,
is->audio_tgt_channel_layout, is->audio_tgt_fmt,
is->audio_tgt_freq, dec_channel_layout,
is->audio_frame->format, is->audio_frame->sample_rate,
0, NULL);
if (!is->swr_ctx || swr_init(is->swr_ctx) < 0) {
fprintf(stderr, "swr_init() failed\n");
break;
}
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;
}

/* 这里我们可以对采样数进行调整，增加或者减少，一般可以用来做声画同步 */
if (is->swr_ctx) {
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) {
if (swr_set_compensation(is->swr_ctx,
(wanted_nb_samples - is->audio_frame->nb_samples)
* is->audio_tgt_freq
/ is->audio_frame->sample_rate,
wanted_nb_samples * is->audio_tgt_freq
/ is->audio_frame->sample_rate) < 0) {
fprintf(stderr, "swr_set_compensation() failed\n");
break;
}
}

len2 = swr_convert(is->swr_ctx, out,
sizeof(is->audio_buf2) / is->audio_tgt_channels
/ av_get_bytes_per_sample(is->audio_tgt_fmt),
in, is->audio_frame->nb_samples);
if (len2 < 0) {
fprintf(stderr, "swr_convert() failed\n");
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\n");
swr_init(is->swr_ctx);
}
is->audio_buf = is->audio_buf2;
resampled_data_size = len2 * is->audio_tgt_channels
* av_get_bytes_per_sample(is->audio_tgt_fmt);
} else {
resampled_data_size = decoded_data_size;
is->audio_buf = is->audio_frame->data[0];
}

pts = is->audio_clock;
*pts_ptr = pts;
n = 2 * is->audio_st->codec->channels;
is->audio_clock += (double) resampled_data_size
/ (double) (n * is->audio_st->codec->sample_rate);

// We have data, return it and come back for more later
return resampled_data_size;
}

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;

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

/* if update, update the audio clock w/pts */
if (pkt->pts != AV_NOPTS_VALUE) {
is->audio_clock = av_q2d(is->audio_st->time_base) * pkt->pts;
}
}

return 0;
}

void audio_callback(void *userdata, Uint8 *stream, int len) {
VideoState *is = (VideoState *) userdata;
int len1, audio_data_size;

double pts;

/*   len是由SDL传入的SDL缓冲区的大小，如果这个缓冲未满，我们就一直往里填充数据 */
while (len > 0) {
/*  audio_buf_index 和 audio_buf_size 标示我们自己用来放置解码出来的数据的缓冲区，*/
/*   这些数据待copy到SDL缓冲区， 当audio_buf_index >= audio_buf_size的时候意味着我*/
/*   们的缓冲为空，没有数据可供copy，这时候需要调用audio_decode_frame来解码出更
/*   多的桢数据 */

if (is->audio_buf_index >= is->audio_buf_size) {
audio_data_size = audio_decode_frame(is, &pts);
/* audio_data_size < 0 标示没能解码出数据，我们默认播放静音 */
if (audio_data_size < 0) {
/* silence */
is->audio_buf_size = 1024;
/* 清零，静音 */
memset(is->audio_buf, 0, is->audio_buf_size);
} else {
is->audio_buf_size = audio_data_size;
}
is->audio_buf_index = 0;
}
/*  查看stream可用空间，决定一次copy多少数据，剩下的下次继续copy */
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;
}
}

static Uint32 sdl_refresh_timer_cb(Uint32 interval, void *opaque) {
SDL_Event event;
event.type = FF_REFRESH_EVENT;
event.user.data1 = opaque;
SDL_PushEvent(&event);
return 0;
}

static void schedule_refresh(VideoState *is, int delay) {
SDL_AddTimer(delay, sdl_refresh_timer_cb, is);
}

int decode_interrupt_cb(void *opaque) {
return (global_video_state && global_video_state->quit);
}

void video_display(VideoState *is) {
SDL_Rect rect;
VideoPicture *vp;
float aspect_ratio;

vp = &is->pictq[is->pictq_rindex];
if (vp->bmp) {
if (is->video_st->codec->sample_aspect_ratio.num == 0) {
aspect_ratio = 0;
} else {
aspect_ratio = av_q2d(is->video_st->codec->sample_aspect_ratio)
* is->video_st->codec->width / is->video_st->codec->height;
}

if (aspect_ratio <= 0.0) {
aspect_ratio = (float) is->video_st->codec->width
/ (float) is->video_st->codec->height;
}

rect.x = 0;
rect.y = 0;
rect.w = vp->width;
rect.h = vp->height;

SDL_UpdateYUVTexture(vp->bmp, &rect, vp->rawdata->data[0],
vp->rawdata->linesize[0], vp->rawdata->data[1],
vp->rawdata->linesize[1], vp->rawdata->data[2],
vp->rawdata->linesize[2]);

SDL_RenderClear(vp->renderer);
SDL_RenderCopy(vp->renderer, vp->bmp, &rect, &rect);
SDL_RenderPresent(vp->renderer);
}
}

void video_refresh_timer(void *userdata) {
VideoState *is = (VideoState *) userdata;
VideoPicture *vp;
double actual_delay, delay, sync_threshold, ref_clock, diff;

if (is->video_st) {
if (is->pictq_size == 0) {
schedule_refresh(is, 1);
} else {
vp = &is->pictq[is->pictq_rindex];

delay = vp->pts - is->frame_last_pts; /* the pts from last time */
if (delay <= 0 || delay >= 1.0) {
/* if incorrect delay, use previous one */
delay = is->frame_last_delay;
}
/* save for next time */
is->frame_last_delay = delay;
is->frame_last_pts = vp->pts;

/* update delay to sync to audio */
ref_clock = get_audio_clock(is);
diff = vp->pts - ref_clock;

/* Skip or repeat the frame. Take delay into account
FFPlay still doesn't "know if this is the best guess." */
sync_threshold =
(delay > AV_SYNC_THRESHOLD) ? delay : AV_SYNC_THRESHOLD;
if (fabs(diff) < AV_NOSYNC_THRESHOLD) {
if (diff <= -sync_threshold) {
delay = 0;
} else if (diff >= sync_threshold) {
delay = 2 * delay;
}
}
is->frame_timer += delay;
/* computer the REAL delay */
actual_delay = is->frame_timer - (av_gettime() / 1000000.0);
if (actual_delay < 0.010) {
/* Really it should skip the picture instead */
actual_delay = 0.010;
}
schedule_refresh(is, (int) (actual_delay * 1000 + 0.5));

/* show the picture! */
video_display(is);

/* update queue for next picture! */
if (++is->pictq_rindex == VIDEO_PICTURE_QUEUE_SIZE) {
is->pictq_rindex = 0;
}
SDL_LockMutex(is->pictq_mutex);
is->pictq_size--;
SDL_CondSignal(is->pictq_cond);
SDL_UnlockMutex(is->pictq_mutex);
}
} else {
schedule_refresh(is, 100);
}
}

void alloc_picture(void *userdata) {
VideoState *is = (VideoState *) userdata;
VideoPicture *vp;

vp = &is->pictq[is->pictq_windex];
if (vp->bmp) {
// we already have one make another, bigger/smaller
SDL_DestroyTexture(vp->bmp);
}

if(vp->rawdata) {
av_free(vp->rawdata);
}

// Allocate a place to put our YUV image on that screen
vp->screen = SDL_CreateWindow("My Player Window", SDL_WINDOWPOS_UNDEFINED,
SDL_WINDOWPOS_UNDEFINED, is->video_st->codec->width,
is->video_st->codec->height,
SDL_WINDOW_FULLSCREEN | SDL_WINDOW_OPENGL);

vp->renderer = SDL_CreateRenderer(vp->screen, -1, 0);
vp->bmp = SDL_CreateTexture(vp->renderer, SDL_PIXELFORMAT_YV12,
SDL_TEXTUREACCESS_STREAMING, is->video_st->codec->width, is->video_st->codec->height);

vp->width = is->video_st->codec->width;
vp->height = is->video_st->codec->height;

AVFrame* pFrameYUV = avcodec_alloc_frame();
if (pFrameYUV == NULL)
return;

int numBytes = avpicture_get_size(PIX_FMT_YUV420P, vp->width,
vp->height);

uint8_t* buffer = (uint8_t *) av_malloc(numBytes * sizeof(uint8_t));

avpicture_fill((AVPicture *) pFrameYUV, buffer, PIX_FMT_YUV420P,
vp->width, vp->height);

vp->rawdata = pFrameYUV;

SDL_LockMutex(is->pictq_mutex);
vp->allocated = 1;
SDL_CondSignal(is->pictq_cond);
SDL_UnlockMutex(is->pictq_mutex);
}

int queue_picture(VideoState *is, AVFrame *pFrame, double pts) {
VideoPicture *vp;
//int dst_pic_fmt
AVPicture pict;

/* wait unitl we have space for a new pic */
SDL_LockMutex(is->pictq_mutex);
while (is->pictq_size >= VIDEO_PICTURE_QUEUE_SIZE && !is->quit) {
SDL_CondWait(is->pictq_cond, is->pictq_mutex);
}
SDL_UnlockMutex(is->pictq_mutex);

if (is->quit)
return -1;

// windex is set to 0 initially
vp = &is->pictq[is->pictq_windex];

/* allocate or resize the buffer ! */
if (!vp->bmp || vp->width != is->video_st->codec->width
|| vp->height != is->video_st->codec->height) {
SDL_Event event;

vp->allocated = 0;
/* we have to do it in the main thread */
event.type = FF_ALLOC_EVENT;
event.user.data1 = is;
SDL_PushEvent(&event);

/* wait until we have a picture allocated */
SDL_LockMutex(is->pictq_mutex);
while (!vp->allocated && !is->quit) {
SDL_CondWait(is->pictq_cond, is->pictq_mutex);
}
}
SDL_UnlockMutex(is->pictq_mutex);
if (is->quit) {
return -1;
}

/* We have a place to put our picture on the queue */
if (vp->rawdata) {
// Convert the image into YUV format that SDL uses
sws_scale(is->sws_ctx, (uint8_t const * const *) pFrame->data,
pFrame->linesize, 0, is->video_st->codec->height,
vp->rawdata->data, vp->rawdata->linesize);

vp->pts = pts;

/* now we inform our display thread that we have a pic ready */
if (++is->pictq_windex == VIDEO_PICTURE_QUEUE_SIZE) {
is->pictq_windex = 0;
}
SDL_LockMutex(is->pictq_mutex);
is->pictq_size++;
SDL_UnlockMutex(is->pictq_mutex);
}
return 0;
}

double synchronize_video(VideoState *is, AVFrame *src_frame, double pts) {

double frame_delay;

if (pts != 0) {
/* if we have pts, set video clock to it */
is->video_clock = pts;
} else {
/* if we aren't given a pts, set it to the clock */
pts = is->video_clock;
}
/* update the video clock */
frame_delay = av_q2d(is->video_st->codec->time_base);
/* if we are repeating a frame, adjust clock accordingly */
frame_delay += src_frame->repeat_pict * (frame_delay * 0.5);
is->video_clock += frame_delay;
return pts;
}
uint64_t global_video_pkt_pts = AV_NOPTS_VALUE;

/* These are called whenever we allocate a frame
* buffer. We use this to store the global_pts in
* a frame at the time it is allocated.
*/
int our_get_buffer(struct AVCodecContext *c, AVFrame *pic) {
int ret = avcodec_default_get_buffer(c, pic);
uint64_t *pts = av_malloc(sizeof(uint64_t));
*pts = global_video_pkt_pts;
pic->opaque = pts;
return ret;
}

void our_release_buffer(struct AVCodecContext *c, AVFrame *pic) {
if (pic)
av_freep(&pic->opaque);
avcodec_default_release_buffer(c, pic);
}

int video_thread(void *arg) {
VideoState *is = (VideoState *) arg;
AVPacket pkt1, *packet = &pkt1;
int frameFinished;
AVFrame *pFrame;

double pts;

pFrame = av_frame_alloc();

for (;;) {
if (packet_queue_get(&is->videoq, packet, 1) < 0) {
// means we quit getting packets
break;
}

pts = 0;

// Save global pts to be stored in pFrame in first call
global_video_pkt_pts = packet->pts;

// Decode video frame
avcodec_decode_video2(is->video_st->codec, pFrame, &frameFinished,
packet);

if (packet->dts == AV_NOPTS_VALUE && pFrame->opaque
&& *(uint64_t*) pFrame->opaque != AV_NOPTS_VALUE) {
pts = *(uint64_t *) pFrame->opaque;
} else if (packet->dts != AV_NOPTS_VALUE) {
pts = packet->dts;
} else {
pts = 0;
}
pts *= av_q2d(is->video_st->time_base);

// Did we get a video frame?
if (frameFinished) {
pts = synchronize_video(is, pFrame, pts);
if (queue_picture(is, pFrame, pts) < 0) {
break;
}
}
av_free_packet(packet);
}

av_free(pFrame);
return 0;
}

int audio_stream_component_open(VideoState *is, int stream_index) {
AVFormatContext *ic = is->ic;
AVCodecContext *codecCtx;
AVCodec *codec;
SDL_AudioSpec wanted_spec, spec;
int64_t wanted_channel_layout = 0;
int wanted_nb_channels;
/*  SDL支持的声道数为 1, 2, 4, 6 */
/*  后面我们会使用这个数组来纠正不支持的声道数目 */
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;
wanted_nb_channels = codecCtx->channels;
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!\n");
return -1;
}
wanted_spec.format = AUDIO_S16SYS; // 具体含义请查看“SDL宏定义”部分
wanted_spec.silence = 0;            // 0指示静音
wanted_spec.samples = SDL_AUDIO_BUFFER_SIZE;  // 自定义SDL缓冲区大小
wanted_spec.callback = audio_callback;        // 音频解码的关键回调函数
wanted_spec.userdata = is;                    // 传给上面回调函数的外带数据

/*  打开音频设备，这里使用一个while来循环尝试打开不同的声道数(由上面 */
/*  next_nb_channels数组指定）直到成功打开，或者全部失败 */
while (SDL_OpenAudio(&wanted_spec, &spec) < 0) {
fprintf(stderr, "SDL_OpenAudio (%d channels): %s\n",
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\n");
return -1;
}
wanted_channel_layout = av_get_default_channel_layout(
wanted_spec.channels);
}

/* 检查实际使用的配置（保存在spec,由SDL_OpenAudio()填充） */
if (spec.format != AUDIO_S16SYS) {
fprintf(stderr, "SDL advised audio format %d is not supported!\n",
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!\n",
spec.channels);
return -1;
}
}

is->audio_hw_buf_size = spec.size;

/* 把设置好的参数保存到大结构中 */
is->audio_src_fmt = is->audio_tgt_fmt = AV_SAMPLE_FMT_S16;
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);
if (!codec || (avcodec_open2(codecCtx, codec, NULL) < 0)) {
fprintf(stderr, "Unsupported codec!\n");
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); // 开始播放静音
break;
default:
break;
}

return 0;
}

int video_stream_component_open(VideoState *is, int stream_index) {
AVFormatContext *pFormatCtx = is->ic;
AVCodecContext *codecCtx;
AVCodec *codec;

if (stream_index < 0 || stream_index >= pFormatCtx->nb_streams) {
return -1;
}

// Get a pointer to the codec context for the video stream
codecCtx = pFormatCtx->streams[stream_index]->codec;

codec = avcodec_find_decoder(codecCtx->codec_id);
if (!codec || (avcodec_open2(codecCtx, codec, NULL) < 0)) {
fprintf(stderr, "Unsupported codec!\n");
return -1;
}

switch (codecCtx->codec_type) {
case AVMEDIA_TYPE_VIDEO:
is->videoStream = stream_index;
is->video_st = pFormatCtx->streams[stream_index];
is->sws_ctx = sws_getContext(is->video_st->codec->width,
is->video_st->codec->height, is->video_st->codec->pix_fmt,
is->video_st->codec->width, is->video_st->codec->height,
AV_PIX_FMT_YUV420P, SWS_FAST_BILINEAR, NULL, NULL, NULL);

is->frame_timer = (double) av_gettime() / 1000000.0;
is->frame_last_delay = 40e-3;

packet_queue_init(&is->videoq);
is->video_tid = SDL_CreateThread(video_thread, "video_thread", is);

codecCtx->get_buffer = our_get_buffer;
codecCtx->release_buffer = our_release_buffer;
break;
default:
break;
}
return 0;
}

int decode_thread(void *arg) {
VideoState *is = (VideoState *) arg;
AVFormatContext *pFormatCtx = NULL;
AVPacket pkt1, *packet = &pkt1;

int video_index = -1;
int audio_index = -1;
int i;

is->videoStream = -1;
is->audioStream = -1;

AVIOInterruptCB interupt_cb;

global_video_state = is;

// will interrup blocking functions if we quit!
interupt_cb.callback = decode_interrupt_cb;
interupt_cb.opaque = is;

if (avio_open2(&is->io_ctx, is->filename, 0, &interupt_cb, NULL)) {
fprintf(stderr, "Cannot open I/O for %s\n", is->filename);
return -1;
}

//Open video file
if (avformat_open_input(&pFormatCtx, is->filename, NULL, NULL) != 0) {
return -1; //Couldn't open file
}

is->ic = pFormatCtx;

//Retrieve stream infomation
if (avformat_find_stream_info(pFormatCtx, NULL) < 0) {
return -1; // Couldn't find stream information
}

//Dump information about file onto standard error
av_dump_format(pFormatCtx, 0, is->filename, 0);

//Find the first video stream
for (i = 0; i < pFormatCtx->nb_streams; i++) {
if (pFormatCtx->streams[i]->codec->coder_type == AVMEDIA_TYPE_VIDEO
&& video_index < 0) {
video_index = i;
}

if (pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_AUDIO
&& audio_index < 0) {
audio_index = i;
}
}

if (audio_index >= 0) {
/* 所有设置SDL音频流信息的步骤都在这个函数里完成 */
audio_stream_component_open(is, audio_index);
}

if (video_index >= 0) {
video_stream_component_open(is, video_index);
}

if (is->videoStream < 0 || is->audioStream <= 0) {
fprintf(stderr, "%s: could not open codec\n", is->filename);
goto fail;
}

//main decode loop
/* 读包的主循环， av_read_frame不停的从文件中读取数据包*/
for (;;) {
if (is->quit) {
break;
}

//seek  stuff goes here
/* 这里audioq.size是指队列中的所有数据包带的音频数据的总量或者视频数据总量，并不是包的数量 */
if (is->audioq.size > MAX_AUDIO_SIZE || is->videoq.size > MAX_VIDEO_SIZE) {
SDL_Delay(10);
continue;
}
if (av_read_frame(is->ic, packet) < 0) {
if (is->ic->pb->error == 0) {
SDL_Delay(100); /* no error; wait for user input */
continue;
} else {
break;
}
}
// Is this a packet from the video stream?
if (packet->stream_index == is->videoStream) {
packet_queue_put(&is->videoq, packet);
} else if (packet->stream_index == is->audioStream) {
packet_queue_put(&is->audioq, packet);
} else {
av_free_packet(packet);
}
}

/*all done - wait for it*/
while (!is->quit) {
SDL_Delay(100);
}

fail: if (1) {
SDL_Event event;
event.type = FF_QUIT_EVENT;
event.user.data1 = is;
SDL_PushEvent(&event);
}
return 0;
}

int main(int argc, char *argv[]) {
char *filename = argv[1];
SDL_Event event;

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

// Register all formats and codecs
av_register_all();

if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER)) {
fprintf(stderr, "Could not initialize SDL - %s\n", SDL_GetError());
exit(1);
}

av_strlcpy(is->filename, filename, sizeof(is->filename));

is->pictq_mutex = SDL_CreateMutex();
is->pictq_cond = SDL_CreateCond();

schedule_refresh(is, 40);

is->parse_tid = SDL_CreateThread(decode_thread, "parse_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:
SDL_CondSignal(is->audioq.cond);
SDL_CondSignal(is->videoq.cond);
is->quit = 1;
SDL_Quit();
return 0;
break;
case FF_ALLOC_EVENT:
alloc_picture(event.user.data1);
break;

case FF_REFRESH_EVENT:
video_refresh_timer(event.user.data1);
break;
}
}

return 0;
}