ffplay.c数据结构分析

本文主要是介绍ffplay.c数据结构分析，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

最近在做流媒体播放器的优化，参考了ffplay.c的代码，主要对存储和流程上做下解剖。


数据存储
15M的QUEUE
#define MAX_QUEUE_SIZE (15 * 1024 * 1024)

typedef struct MyAVPacketList {
    AVPacket pkt;
    struct MyAVPacketList *next;
    int serial;
} MyAVPacketList;

typedef struct PacketQueue {
    MyAVPacketList *first_pkt, *last_pkt;
    int nb_packets;
    int size;
    int abort_request;
    int serial;
    SDL_mutex *mutex;
    SDL_cond *cond;

} PacketQueue;

typedef struct FrameQueue {
    Frame queue[FRAME_QUEUE_SIZE];
    int rindex;
    int windex;
    int size;
    int max_size;
    int keep_last;
    int rindex_shown;
    SDL_mutex *mutex;
    SDL_cond *cond;
    PacketQueue *pktq;
} FrameQueue;


解码播放流程：

读线程：
is->read_tid     = SDL_CreateThread(read_thread, is);/* this thread gets the stream from the disk or the network */
主要作用是读取一帧编码后的数据，然后入队


ret = av_read_frame(ic, pkt);
packet_queue_put(&is->videoq, pkt);

入队代码：

static int packet_queue_put_private(PacketQueue *q, AVPacket *pkt)
{MyAVPacketList *pkt1;if (q->abort_request)return -1;pkt1 = av_malloc(sizeof(MyAVPacketList));if (!pkt1)return -1;pkt1->pkt = *pkt;pkt1->next = NULL;if (pkt == &flush_pkt)q->serial++;pkt1->serial = q->serial;if (!q->last_pkt)q->first_pkt = pkt1;elseq->last_pkt->next = pkt1;q->last_pkt = pkt1;q->nb_packets++;q->size += pkt1->pkt.size + sizeof(*pkt1);/* XXX: should duplicate packet data in DV case */SDL_CondSignal(q->cond);return 0;
}static int packet_queue_put(PacketQueue *q, AVPacket *pkt)
{int ret;/* duplicate the packet */if (pkt != &flush_pkt && av_dup_packet(pkt) < 0)return -1;SDL_LockMutex(q->mutex);ret = packet_queue_put_private(q, pkt);SDL_UnlockMutex(q->mutex);if (pkt != &flush_pkt && ret < 0)av_free_packet(pkt);return ret;
}

解码线程：

decoder_init(&is->auddec, avctx, &is->audioq, is->continue_read_thread);
decoder_start(&is->auddec, audio_thread, is);


decoder_init(&is->viddec, avctx, &is->videoq, is->continue_read_thread);
decoder_start(&is->viddec, video_thread, is);
video_thread的流程：
get_video_frame 然后去刷新界面
for (;;) {
ret = get_video_frame(is, frame);
}

get_video_frame是解码后得到一帧：
if ((got_picture = decoder_decode_frame(&is->viddec, frame, NULL)) < 0)
decoder_decode_frame是得到从packet_queue_get中得到一个packet并扔给解码器解码：
if (packet_queue_get(d->queue, &pkt, 1, &d->pkt_serial) < 0)
return -1;  

packet_queue_get是等待信号量直到得到一个pkt：

/* return < 0 if aborted, 0 if no packet and > 0 if packet.  */
static int packet_queue_get(PacketQueue *q, AVPacket *pkt, int block, int *serial)
{MyAVPacketList *pkt1;int ret;SDL_LockMutex(q->mutex);for (;;) {if (q->abort_request) {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 + sizeof(*pkt1);*pkt = pkt1->pkt;if (serial)*serial = pkt1->serial;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;
}

分析完了。

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