[置顶] 最新版（2013.01.17）x264的多线程代码研究（一）

先罗列出代码中与多线程有关的宏定义、结构体、变量、函数等，锁定为需要重点关注的对象，在接下来的研究中逐步深入探讨这些对象的含义和作用。

define X264_THREAD_MAX 128
#define X264_LOOKAHEAD_THREAD_MAX 16

#define X264_LOOKAHEAD_MAX 250

// arbitrary, but low because SATD scores are 1/4 normal
#define X264_LOOKAHEAD_QP (12+QP_BD_OFFSET)

// number of pixels (per thread) in progress at any given time.
// 16 for the macroblock in progress + 3 for deblocking + 3 for motion compensation filter + 2 for extra safety
#define X264_THREAD_HEIGHT 24
#define x264_pthread_t               pthread_t
#define x264_pthread_create          pthread_create
#define x264_pthread_join            pthread_join
#define x264_pthread_mutex_t         pthread_mutex_t
#define x264_pthread_mutex_init      pthread_mutex_init
#define x264_pthread_mutex_destroy   pthread_mutex_destroy
#define x264_pthread_mutex_lock      pthread_mutex_lock
#define x264_pthread_mutex_unlock    pthread_mutex_unlock
#define x264_pthread_cond_t          pthread_cond_t
#define x264_pthread_cond_init       pthread_cond_init
#define x264_pthread_cond_destroy    pthread_cond_destroy
#define x264_pthread_cond_broadcast  pthread_cond_broadcast
#define x264_pthread_cond_wait       pthread_cond_wait
#define x264_pthread_attr_t          pthread_attr_t
#define x264_pthread_attr_init       pthread_attr_init
#define x264_pthread_attr_destroy    pthread_attr_destroy
#define x264_pthread_num_processors_np pthread_num_processors_np
#define X264_PTHREAD_MUTEX_INITIALIZER PTHREAD_MUTEX_INITIALIZER
typedef struct x264_lookahead_t
{
    volatile uint8_t              b_exit_thread;
    uint8_t                       b_thread_active;
    uint8_t                       b_analyse_keyframe;
    int                           i_last_keyframe;
    int                           i_slicetype_length;
    x264_frame_t                  *last_nonb;
    x264_pthread_t                thread_handle;
    x264_sync_frame_list_t        ifbuf;
    x264_sync_frame_list_t        next;
    x264_sync_frame_list_t        ofbuf;
} x264_lookahead_t;
/* synchronized frame list */
typedef struct
{
   x264_frame_t **list;
   int i_max_size;
   int i_size;
   x264_pthread_mutex_t     mutex;
   x264_pthread_cond_t      cv_fill;  /* event signaling that the list became fuller */
   x264_pthread_cond_t      cv_empty; /* event signaling that the list became emptier */
} x264_sync_frame_list_t;
typedef struct x264_frame //!< 为节省篇幅，仅附上与线程有关的成员变量
{
    /* threading */
    int     i_lines_completed; /* in pixels */
    int     i_lines_weighted; /* FIXME: this only supports weighting of one reference frame */
    int     i_reference_count; /* number of threads using this frame (not necessarily the number of pointers) */
    x264_pthread_mutex_t mutex;
    x264_pthread_cond_t  cv;

} x264_frame_t;
/* threading */
void x264_frame_cond_broadcast( x264_frame_t *frame, int i_lines_completed )
{
    x264_pthread_mutex_lock( &frame->mutex );
    frame->i_lines_completed = i_lines_completed;
    x264_pthread_cond_broadcast( &frame->cv );
    x264_pthread_mutex_unlock( &frame->mutex );
}

void x264_frame_cond_wait( x264_frame_t *frame, int i_lines_completed )
{
    x264_pthread_mutex_lock( &frame->mutex );
    while( frame->i_lines_completed < i_lines_completed )
        x264_pthread_cond_wait( &frame->cv, &frame->mutex );
    x264_pthread_mutex_unlock( &frame->mutex );
}

void x264_threadslice_cond_broadcast( x264_t *h, int pass )
{
    x264_pthread_mutex_lock( &h->mutex );
    h->i_threadslice_pass = pass;
    if( pass > 0 )
        x264_pthread_cond_broadcast( &h->cv );
    x264_pthread_mutex_unlock( &h->mutex );
}

void x264_threadslice_cond_wait( x264_t *h, int pass )
{
    x264_pthread_mutex_lock( &h->mutex );
    while( h->i_threadslice_pass < pass )
        x264_pthread_cond_wait( &h->cv, &h->mutex );
    x264_pthread_mutex_unlock( &h->mutex );
}
int x264_sync_frame_list_init( x264_sync_frame_list_t *slist, int max_size )
{
    if( max_size < 0 )
        return -1;
    slist->i_max_size = max_size;
    slist->i_size = 0;
    CHECKED_MALLOCZERO( slist->list, (max_size+1) * sizeof(x264_frame_t*) );
    if( x264_pthread_mutex_init( &slist->mutex, NULL ) ||
        x264_pthread_cond_init( &slist->cv_fill, NULL ) ||
        x264_pthread_cond_init( &slist->cv_empty, NULL ) )
        return -1;
    return 0;
fail:
    return -1;
}

void x264_sync_frame_list_delete( x264_sync_frame_list_t *slist )
{
    x264_pthread_mutex_destroy( &slist->mutex );
    x264_pthread_cond_destroy( &slist->cv_fill );
    x264_pthread_cond_destroy( &slist->cv_empty );
    x264_frame_delete_list( slist->list );
}

void x264_sync_frame_list_push( x264_sync_frame_list_t *slist, x264_frame_t *frame )
{
    x264_pthread_mutex_lock( &slist->mutex );
    while( slist->i_size == slist->i_max_size )
        x264_pthread_cond_wait( &slist->cv_empty, &slist->mutex );
    slist->list[ slist->i_size++ ] = frame;
    x264_pthread_mutex_unlock( &slist->mutex );
    x264_pthread_cond_broadcast( &slist->cv_fill );
}

x264_frame_t *x264_sync_frame_list_pop( x264_sync_frame_list_t *slist )
{
    x264_frame_t *frame;
    x264_pthread_mutex_lock( &slist->mutex );
    while( !slist->i_size )
        x264_pthread_cond_wait( &slist->cv_fill, &slist->mutex );
    frame = slist->list[ --slist->i_size ];
    slist->list[ slist->i_size ] = NULL;
    x264_pthread_cond_broadcast( &slist->cv_empty );
    x264_pthread_mutex_unlock( &slist->mutex );
    return frame;
}                                                                                                                                   
typedef struct x264_param_t //!< 为节省篇幅，仅附上与线程有关的成员变量
{
    /* CPU flags */
    unsigned int cpu;
    int         i_threads;           /* encode multiple frames in parallel */
    int         i_lookahead_threads; /* multiple threads for lookahead analysis */
    int         b_sliced_threads;  /* Whether to use slice-based threading. */
    int         b_deterministic; /* whether to allow non-deterministic optimizations when threaded */
    int         b_cpu_independent; /* force canonical behavior rather than cpu-dependent optimal algorithms */
    int         i_sync_lookahead; /* threaded lookahead buffer */
}x264_param_t; 
struct x264_t //!< 为节省篇幅，仅附上与线程有关的成员变量
{
    /* encoder parameters */
    x264_param_t    param;

    x264_t          *thread[X264_THREAD_MAX+1];
    x264_t          *lookahead_thread[X264_LOOKAHEAD_THREAD_MAX];
    int             b_thread_active;
    int             i_thread_phase; /* which thread to use for the next frame */
    int             i_thread_idx;   /* which thread this is */
    int             i_threadslice_start; /* first row in this thread slice */
    int             i_threadslice_end; /* row after the end of this thread slice */
    int             i_threadslice_pass; /* which pass of encoding we are on */
    x264_threadpool_t *threadpool;
    x264_threadpool_t *lookaheadpool;
    x264_pthread_mutex_t mutex;
    x264_pthread_cond_t cv;
}