一 参数配置 parse_stream_params
} else if (arg_match(&arg, &g_av1_codec_arg_defs.threads, argi)) {
config->cfg.g_threads = arg_parse_uint(&arg);
二 使用线程个数参数g_threads
int av1_compute_num_fp_contexts(AV1_PRIMARY *ppi, AV1EncoderConfig *oxcf)
{
//将帧编码模块的并行工作线程数量初始化为0
ppi->p_mt_info.num_mod_workers[MOD_FRAME_ENC] = 0;
//检查帧并行多线程配置是否有效，如果无效，直接返回1（表示单帧处理）
if (!av1_check_fpmt_config(ppi, oxcf)) {
return 1;
}
//计算最大编码工作线程数
int max_num_enc_workers = compute_max_num_enc_workers(
&ppi->cpi->common.mi_params, ppi->cpi->common.seq_params->mib_size_log2);
//用于调整每个帧的工作线程数量计算的缩放因子和舍入因子
// Scaling factors and rounding factors used to tune worker_per_frame
// computation.
int rounding_factor[2] = { 2, 4 };
int scaling_factor[2] = { 4, 8 };
//判断视频分辨率是否为480p或者更低
int is_480p_or_lesser =
AOMMIN(oxcf->frm_dim_cfg.width, oxcf->frm_dim_cfg.height) <= 480;
int is_sb_64 = 0;
//判断视频分辨率是否为480p或者更低
if (ppi->cpi != NULL)
is_sb_64 = ppi->cpi->common.seq_params->sb_size == BLOCK_64X64;
//根据分辨率和超级块大小选择合适的索引，对于大于480p而且超级块大小为64x64的情况，使用索引1，否则使用索引0
// A parallel frame encode has at least 1/4th the
// theoretical limit of max enc workers in default case. For resolutions
// larger than 480p, if SB size is 64x64, optimal performance is obtained with
// limit of 1/8.
int index = (!is_480p_or_lesser && is_sb_64) ? 1 : 0;
//计算每个帧的工作线程数，确保至少为1
int workers_per_frame =
AOMMAX(1, (max_num_enc_workers + rounding_factor[index]) /
scaling_factor[index]);
//获取最大线程数量
int max_threads = oxcf->max_threads;
//计算帧并行上下文的数量
int num_fp_contexts = max_threads / workers_per_frame;
//如果使用多块编码 tile encoding
// Based on empirical results, FPMT gains with multi-tile are significant when
// more parallel frames are available. Use FPMT with multi-tile encode only
// when sufficient threads are available for parallel encode of
// MAX_PARALLEL_FRAMES frames.
if (oxcf->tile_cfg.tile_columns > 0 || oxcf->tile_cfg.tile_rows > 0) {
//当并行帧的数量小于MAX_PARALLEL_FRAMES时，将帧并行上下文数量设置为1
if (num_fp_contexts < MAX_PARALLEL_FRAMES) num_fp_contexts = 1;
}
//确保帧并行上下文数量在1到MAX_PARALLEL_FRAMES 之间
num_fp_contexts = AOMMAX(1, AOMMIN(num_fp_contexts, MAX_PARALLEL_FRAMES));
//如果ppi->num_fp_contexts为1，则保持计算出num_fp_contexts 不变
//否则，将num_fp_contexts限制为ppi->num_fp_contexts和当前计算值中的较小值
// Limit recalculated num_fp_contexts to ppi->num_fp_contexts.
num_fp_contexts = (ppi->num_fp_contexts == 1)
? num_fp_contexts
: AOMMIN(num_fp_contexts, ppi->num_fp_contexts);
//如果帧并行上下文数量大于1
if (num_fp_contexts > 1) {
//计算帧编码模块的并行工作线程数量，确保不超过最大线程数
ppi->p_mt_info.num_mod_workers[MOD_FRAME_ENC] =
AOMMIN(max_num_enc_workers * num_fp_contexts, oxcf->max_threads);
}
//返回计算出的帧并行上下文数量
return num_fp_contexts;
}
2.10 compute_num_enc_row_mt_workers
// Computes the number of workers for row multi-threading of encoding stage
// 计算编码阶段行多线程的工作线程数
static inline int compute_num_enc_row_mt_workers(const AV1_COMMON *cm,
int max_threads) {
// 定义一个TileInfo结构体变量，用于存储瓦片（tile）信息
TileInfo tile_info;
// 获取视频帧中瓦片的列数
const int tile_cols = cm->tiles.cols;
// 获取视频帧中瓦片的行数
const int tile_rows = cm->tiles.rows;
// 初始化行多线程的总线程数为0
int total_num_threads_row_mt = 0;
// 遍历每一行瓦片
for (int row = 0; row < tile_rows; row++) {
// 遍历每一列瓦片
for (int col = 0; col < tile_cols; col++) {
// 初始化当前瓦片的信息
av1_tile_init(&tile_info, cm, row, col);
// 获取当前瓦片中超级块（super block）的行数
const int num_sb_rows_in_tile = av1_get_sb_rows_in_tile(cm, &tile_info);
// 获取当前瓦片中超级块的列数
const int num_sb_cols_in_tile = av1_get_sb_cols_in_tile(cm, &tile_info);
// 计算当前瓦片可用于行多线程的线程数，并累加到总线程数中
// AOMMIN((num_sb_cols_in_tile + 1) >> 1, num_sb_rows_in_tile)
// 这一步是取 (超级块列数 + 1) 右移一位 和 超级块行数 中的较小值
total_num_threads_row_mt +=
AOMMIN((num_sb_cols_in_tile + 1) >> 1, num_sb_rows_in_tile);
}
}
// 返回总线程数和最大线程数中的较小值
return AOMMIN(max_threads, total_num_threads_row_mt);
}