libaom 源码分析线程结构

一 libaom线程启动函数

void av1_create_workers(AV1_PRIMARY *ppi, int num_workers)

{

PrimaryMultiThreadInfo *const p_mt_info = &ppu->p_mt_info;

const AVxWorkerInterface *const = winterface = aom_get_worker_interface();

for (int i = 0; i < num_workers; ++i) {

AVxWorker* const worker = &p_mt_info->workers[i];

EncWorkerData *const thread_data = &p_mt_info->tile_thr_data[i];

winterface->init(worker);

worker->thread_nae = "aom enc worker";

thread_data->thread_id = i;

thread_data->start = i;

if (i > 0) {

if (!winterface->reset(worker))

aom_internal_error(&ppi->error, AOM_CODEC_ERROR, "Tile encoder thread creation failed");

}

}

winterface->sync(worker);

++p_mt_info->num_workers;

}

二 libaom线程调用栈

#0 in full_pixel_diamond()

#1 0x000000000058ee91 in av1_full_pixel_search ()

firstpass_inter_prediction->first_pass_motion_search

#2 0x000000000057d22c in av1_first_pass_row ()

#3 0x0000000000571124 in fp_enc_row_mt_worker_hook ()

#4 0x0000000000be5ef7 in execute ()

#5 0x00000000005788c8 in av1_fp_encode_tiles_row_mt ()

#6 0x000000000057ea03 in av1_first_pass ()

#7 0x00000000005625c0 in av1_encode ()

#8 0x0000000000c8036f in av1_encode_strategy ()

#9 0x00000000005636eb in av1_get_compressed_data ()

#10 0x00000000004ff0fb in encoder_encode ()

#11 0x00000000004bca0a in aom_codec_encode ()

#12 0x000000000040af05 in encode_frame.isra ()

#13 0x000000000040786c in main ()

三 libaom 线程调用关系

void av1_first_pass_row(AV1_COMP *cpi, ThreadData *td, TileDataEnc *tile_data, const int unit_row, const BLOCK_SIZE fp_block_size) ->

firstpass_inter_prediction(cpi, td, last_frame, golden_frame, unit_row, unit_col, recon_yoffset, recon_uvoffset, src_yoffset, fp_block_size, this_intra_error, raw_motion_err_counts, raw_motion_err_list, best_ref_mv, &best_ref_mv, &last_mv, mb_stats);

firstpass_intra_prediction()

线程入口函数

//定义一个静态的整型函数，用于多线程编码的工作钩子

static int fp_enc_row_mt_worker_hook(void *arg1, void *unused)

{

//将传入的arg1转换为EncWorkerData类型，这个结构体包含了线程的数据

EncWorkerData *const thread_data = (EncWorkerData*)arg1;

//从线程数据中获取编码器的上下文结构

AV1_COMP* const cpi = thread_data->cpi;

//获取当前线程的ID

int thread_id = thread_data->thread_id;

//获取编码器的多线程信息

AV1EncRowMultiThreadInfo *const enc_row_mt = &cpi->mt_info.enc_row_mt;

//如果配置了多线程，获取行多线程互斥锁

//获取线程数据中的内部错误信息结构体

struct aom_internal_error_info* const error_info = &thread_data->error_info;

//获取宏块解码器上下文

MACROBLOCK* const xd = &thread_data->td->mb.e_mbd;

//设置宏块解码器上下文的错误信息

xd->error_info = error_info;

//设置错误恢复环境，只有在调用setjmp()的函数中才有效

//如果setjmp() 返回非零值，表示发生了错误跳转。

if (setjmp(error_info->jmp)) {

error_info->setjmp = 0;

pthread_mutext_lock(enc_ro_mt_mutex_);

//设置firstpass_mt_exit为true, 表示第一个通过多线程退出

enc_row_mt->firstpass_mt_exit = true;

//解锁互斥锁

pthread_mutex_unlock(enc_row_mt_mutex_);

set_firstpass_encode_done(cpi);

return 0;

}

//设置setjmp字段为1，表示jmp_buf是有效的

error_info->setjmp = 1;

//获取AV1的公共结构体

AV1_COMMON *const cm = *cpi->common;

//获取当前线程对应的tile ID

int cur_tile_id = enc_row_mt->thread_id_to_tile_id[thread_id];

//断言当前tile ID不是-1

assert(cur_tile_id != -1);

//获取固定点块大小

const BLOCK_SIZE fp_block_size = cpi->fp_block_size;

//获取单位高度

const int unit_height = mi_size_high[fp_block_size];

//初始化end of frame为0

int end_of_frame = 0;

while (1) {

//初始化当前MI行

int current_mi_row = -1;

//获取firstpass_mt_exit状态

bool firstpass_mt_exit = enc_row_mt->firstpass_mt_exit;

//如果firstpass_mt_exit为false，并且没有当前tile的工作，查询其他tile的状态并获取下一个工作。

if` `(!firstpass_mt_exit &&` `!get_next_job(&cpi->tile_data[cur_tile_id],`
                                            `&current_mi_row, unit_height))` `{`
      `// 没有当前tile的工作，查询其他tile的状态并获取下一个工作。`
      `switch_tile_and_get_next_job(cm, cpi->tile_data,` `&cur_tile_id,`
                                   `&current_mi_row,` `&end_of_frame,` `1,`
`                                   fp_block_size);`
    `}`
`

//如果firstpass mt exit为true, 或者其他工人不需要进一步的工作，跳出循环，

if (firstpass_mt_exit || ned_of_frame) break;

//获取当前tile的数据

TileDataEnc *const this_tile = &cpi->tile_data[cur_tile_id]

// 获取行多线程同步信息。`
`    AV1EncRowMultiThreadSync *const row_mt_sync =` `&this_tile->row_mt_sync;`
    `// 获取线程数据。`
`    ThreadData *td = thread_data->td;`

    `// 断言current_mi_row不是-1，并且小于当前tile的MI行结束。`
    `assert(current_mi_row !=` `-1` `&&`
`           current_mi_row < this_tile->tile_info.mi_row_end);`

    `// 获取单位高度的对数。`
    `const` `int unit_height_log2 = mi_size_high_log2[fp_block_size];`
    `// 调用av1_first_pass_row函数进行第一通过编码。`
    `av1_first_pass_row(cpi, td, this_tile, current_mi_row >> unit_height_log2,`
`                       fp_block_size);`
`#if CONFIG_MULTITHREAD`
    `// 如果配置了多线程，锁定互斥锁。`
    `pthread_mutex_lock(enc_row_mt_mutex_);`
`#endif`
    `// 减少正在工作的线程数。`
`    row_mt_sync->num_threads_working--;`
`#if CONFIG_MULTITHREAD`
    `// 解锁互斥锁。`
    `pthread_mutex_unlock(enc_row_mt_mutex_);`
`#endif`
  `}`
  `// 重置setjmp字段为0。`
`  error_info->setjmp =` `0;`
  `// 返回1表示成功。`
  `return` `1;`
`

}

}