FFmpeg源码调试：解析H.264 SPS(Sequence Parameter Set)中帧的宽高
来源：互联网 发布：浏览器无法连接网络 编辑：程序博客网 时间：2024/05/29 02:49
http://www.jianshu.com/p/a4a9f171f2cf
版本历史
- 7月29日：新增FFmpeg 3.0源码对SPS的处理分析。
- 7月10日：将2015年12月的代码验证整理成文档。
本文档记录了FFmpeg 3.0源码有关解析H.264(AVC) SPS(Sequence Parameter Set)中处理帧的宽高部分的阅读调试过程，同时对比了ijkplayer解析SPS时遇到的宽高不对问题。
1、FFmpeg 3.0 解析H.264 SPS
FFmpeg 3.0解析SPS的流程如下图所示。
解析SPS流程图
调用栈
解析SPS的代码如下：
int ff_h264_decode_seq_parameter_set(H264Context *h, int ignore_truncation){ int profile_idc, level_idc, constraint_set_flags = 0; unsigned int sps_id; int i, log2_max_frame_num_minus4; SPS *sps; sps = av_mallocz(sizeof(SPS)); if (!sps) return AVERROR(ENOMEM); sps->data_size = h->gb.buffer_end - h->gb.buffer; if (sps->data_size > sizeof(sps->data)) { av_log(h->avctx, AV_LOG_WARNING, "Truncating likely oversized SPS\n"); sps->data_size = sizeof(sps->data); } memcpy(sps->data, h->gb.buffer, sps->data_size); profile_idc = get_bits(&h->gb, 8); constraint_set_flags |= get_bits1(&h->gb) << 0; // constraint_set0_flag constraint_set_flags |= get_bits1(&h->gb) << 1; // constraint_set1_flag constraint_set_flags |= get_bits1(&h->gb) << 2; // constraint_set2_flag constraint_set_flags |= get_bits1(&h->gb) << 3; // constraint_set3_flag constraint_set_flags |= get_bits1(&h->gb) << 4; // constraint_set4_flag constraint_set_flags |= get_bits1(&h->gb) << 5; // constraint_set5_flag skip_bits(&h->gb, 2); // reserved_zero_2bits level_idc = get_bits(&h->gb, 8); sps_id = get_ue_golomb_31(&h->gb); if (sps_id >= MAX_SPS_COUNT) { av_log(h->avctx, AV_LOG_ERROR, "sps_id %u out of range\n", sps_id); goto fail; } sps->sps_id = sps_id; sps->time_offset_length = 24; sps->profile_idc = profile_idc; sps->constraint_set_flags = constraint_set_flags; sps->level_idc = level_idc; sps->full_range = -1; memset(sps->scaling_matrix4, 16, sizeof(sps->scaling_matrix4)); memset(sps->scaling_matrix8, 16, sizeof(sps->scaling_matrix8)); sps->scaling_matrix_present = 0; sps->colorspace = 2; //AVCOL_SPC_UNSPECIFIED if (sps->profile_idc == 100 || // High profile sps->profile_idc == 110 || // High10 profile sps->profile_idc == 122 || // High422 profile sps->profile_idc == 244 || // High444 Predictive profile sps->profile_idc == 44 || // Cavlc444 profile sps->profile_idc == 83 || // Scalable Constrained High profile (SVC) sps->profile_idc == 86 || // Scalable High Intra profile (SVC) sps->profile_idc == 118 || // Stereo High profile (MVC) sps->profile_idc == 128 || // Multiview High profile (MVC) sps->profile_idc == 138 || // Multiview Depth High profile (MVCD) sps->profile_idc == 144) { // old High444 profile sps->chroma_format_idc = get_ue_golomb_31(&h->gb); if (sps->chroma_format_idc > 3U) { avpriv_request_sample(h->avctx, "chroma_format_idc %u", sps->chroma_format_idc); goto fail; } else if (sps->chroma_format_idc == 3) { sps->residual_color_transform_flag = get_bits1(&h->gb); if (sps->residual_color_transform_flag) { av_log(h->avctx, AV_LOG_ERROR, "separate color planes are not supported\n"); goto fail; } } sps->bit_depth_luma = get_ue_golomb(&h->gb) + 8; sps->bit_depth_chroma = get_ue_golomb(&h->gb) + 8; if (sps->bit_depth_chroma != sps->bit_depth_luma) { avpriv_request_sample(h->avctx, "Different chroma and luma bit depth"); goto fail; } if (sps->bit_depth_luma < 8 || sps->bit_depth_luma > 14 || sps->bit_depth_chroma < 8 || sps->bit_depth_chroma > 14) { av_log(h->avctx, AV_LOG_ERROR, "illegal bit depth value (%d, %d)\n", sps->bit_depth_luma, sps->bit_depth_chroma); goto fail; } sps->transform_bypass = get_bits1(&h->gb); decode_scaling_matrices(h, sps, NULL, 1, sps->scaling_matrix4, sps->scaling_matrix8); } else { sps->chroma_format_idc = 1; sps->bit_depth_luma = 8; sps->bit_depth_chroma = 8; } log2_max_frame_num_minus4 = get_ue_golomb(&h->gb); if (log2_max_frame_num_minus4 < MIN_LOG2_MAX_FRAME_NUM - 4 || log2_max_frame_num_minus4 > MAX_LOG2_MAX_FRAME_NUM - 4) { av_log(h->avctx, AV_LOG_ERROR, "log2_max_frame_num_minus4 out of range (0-12): %d\n", log2_max_frame_num_minus4); goto fail; } sps->log2_max_frame_num = log2_max_frame_num_minus4 + 4; sps->poc_type = get_ue_golomb_31(&h->gb); if (sps->poc_type == 0) { // FIXME #define unsigned t = get_ue_golomb(&h->gb); if (t>12) { av_log(h->avctx, AV_LOG_ERROR, "log2_max_poc_lsb (%d) is out of range\n", t); goto fail; } sps->log2_max_poc_lsb = t + 4; } else if (sps->poc_type == 1) { // FIXME #define sps->delta_pic_order_always_zero_flag = get_bits1(&h->gb); sps->offset_for_non_ref_pic = get_se_golomb(&h->gb); sps->offset_for_top_to_bottom_field = get_se_golomb(&h->gb); sps->poc_cycle_length = get_ue_golomb(&h->gb); if ((unsigned)sps->poc_cycle_length >= FF_ARRAY_ELEMS(sps->offset_for_ref_frame)) { av_log(h->avctx, AV_LOG_ERROR, "poc_cycle_length overflow %d\n", sps->poc_cycle_length); goto fail; } for (i = 0; i < sps->poc_cycle_length; i++) sps->offset_for_ref_frame[i] = get_se_golomb(&h->gb); } else if (sps->poc_type != 2) { av_log(h->avctx, AV_LOG_ERROR, "illegal POC type %d\n", sps->poc_type); goto fail; } sps->ref_frame_count = get_ue_golomb_31(&h->gb); if (h->avctx->codec_tag == MKTAG('S', 'M', 'V', '2')) sps->ref_frame_count = FFMAX(2, sps->ref_frame_count); if (sps->ref_frame_count > H264_MAX_PICTURE_COUNT - 2 || sps->ref_frame_count > 16U) { av_log(h->avctx, AV_LOG_ERROR, "too many reference frames %d\n", sps->ref_frame_count); goto fail; } sps->gaps_in_frame_num_allowed_flag = get_bits1(&h->gb); sps->mb_width = get_ue_golomb(&h->gb) + 1; sps->mb_height = get_ue_golomb(&h->gb) + 1; if ((unsigned)sps->mb_width >= INT_MAX / 16 || (unsigned)sps->mb_height >= INT_MAX / 16 || av_image_check_size(16 * sps->mb_width, 16 * sps->mb_height, 0, h->avctx)) { av_log(h->avctx, AV_LOG_ERROR, "mb_width/height overflow\n"); goto fail; } sps->frame_mbs_only_flag = get_bits1(&h->gb); if (!sps->frame_mbs_only_flag) sps->mb_aff = get_bits1(&h->gb); else sps->mb_aff = 0; sps->direct_8x8_inference_flag = get_bits1(&h->gb);#ifndef ALLOW_INTERLACE if (sps->mb_aff) av_log(h->avctx, AV_LOG_ERROR, "MBAFF support not included; enable it at compile-time.\n");#endif sps->crop = get_bits1(&h->gb); if (sps->crop) { unsigned int crop_left = get_ue_golomb(&h->gb); unsigned int crop_right = get_ue_golomb(&h->gb); unsigned int crop_top = get_ue_golomb(&h->gb); unsigned int crop_bottom = get_ue_golomb(&h->gb); int width = 16 * sps->mb_width; int height = 16 * sps->mb_height * (2 - sps->frame_mbs_only_flag); if (h->avctx->flags2 & AV_CODEC_FLAG2_IGNORE_CROP) { av_log(h->avctx, AV_LOG_DEBUG, "discarding sps cropping, original " "values are l:%d r:%d t:%d b:%d\n", crop_left, crop_right, crop_top, crop_bottom); sps->crop_left = sps->crop_right = sps->crop_top = sps->crop_bottom = 0; } else { int vsub = (sps->chroma_format_idc == 1) ? 1 : 0; int hsub = (sps->chroma_format_idc == 1 || sps->chroma_format_idc == 2) ? 1 : 0; int step_x = 1 << hsub; int step_y = (2 - sps->frame_mbs_only_flag) << vsub; if (crop_left & (0x1F >> (sps->bit_depth_luma > 8)) && !(h->avctx->flags & AV_CODEC_FLAG_UNALIGNED)) { crop_left &= ~(0x1F >> (sps->bit_depth_luma > 8)); av_log(h->avctx, AV_LOG_WARNING, "Reducing left cropping to %d " "chroma samples to preserve alignment.\n", crop_left); } if (crop_left > (unsigned)INT_MAX / 4 / step_x || crop_right > (unsigned)INT_MAX / 4 / step_x || crop_top > (unsigned)INT_MAX / 4 / step_y || crop_bottom> (unsigned)INT_MAX / 4 / step_y || (crop_left + crop_right ) * step_x >= width || (crop_top + crop_bottom) * step_y >= height ) { av_log(h->avctx, AV_LOG_ERROR, "crop values invalid %d %d %d %d / %d %d\n", crop_left, crop_right, crop_top, crop_bottom, width, height); goto fail; } sps->crop_left = crop_left * step_x; sps->crop_right = crop_right * step_x; sps->crop_top = crop_top * step_y; sps->crop_bottom = crop_bottom * step_y; } } else { sps->crop_left = sps->crop_right = sps->crop_top = sps->crop_bottom = sps->crop = 0; } sps->vui_parameters_present_flag = get_bits1(&h->gb); if (sps->vui_parameters_present_flag) { int ret = decode_vui_parameters(h, sps); if (ret < 0) goto fail; } if (get_bits_left(&h->gb) < 0) { av_log(h->avctx, ignore_truncation ? AV_LOG_WARNING : AV_LOG_ERROR, "Overread %s by %d bits\n", sps->vui_parameters_present_flag ? "VUI" : "SPS", -get_bits_left(&h->gb)); if (!ignore_truncation) goto fail; } /* if the maximum delay is not stored in the SPS, derive it based on the * level */ if (!sps->bitstream_restriction_flag) { sps->num_reorder_frames = MAX_DELAYED_PIC_COUNT - 1; for (i = 0; i < FF_ARRAY_ELEMS(level_max_dpb_mbs); i++) { if (level_max_dpb_mbs[i][0] == sps->level_idc) { sps->num_reorder_frames = FFMIN(level_max_dpb_mbs[i][1] / (sps->mb_width * sps->mb_height), sps->num_reorder_frames); break; } } } if (!sps->sar.den) sps->sar.den = 1; if (h->avctx->debug & FF_DEBUG_PICT_INFO) { static const char csp[4][5] = { "Gray", "420", "422", "444" }; av_log(h->avctx, AV_LOG_DEBUG, "sps:%u profile:%d/%d poc:%d ref:%d %dx%d %s %s crop:%u/%u/%u/%u %s %s %"PRId32"/%"PRId32" b%d reo:%d\n", sps_id, sps->profile_idc, sps->level_idc, sps->poc_type, sps->ref_frame_count, sps->mb_width, sps->mb_height, sps->frame_mbs_only_flag ? "FRM" : (sps->mb_aff ? "MB-AFF" : "PIC-AFF"), sps->direct_8x8_inference_flag ? "8B8" : "", sps->crop_left, sps->crop_right, sps->crop_top, sps->crop_bottom, sps->vui_parameters_present_flag ? "VUI" : "", csp[sps->chroma_format_idc], sps->timing_info_present_flag ? sps->num_units_in_tick : 0, sps->timing_info_present_flag ? sps->time_scale : 0, sps->bit_depth_luma, sps->bitstream_restriction_flag ? sps->num_reorder_frames : -1 ); } sps->new = 1; av_free(h->sps_buffers[sps_id]); h->sps_buffers[sps_id] = sps; return 0;fail: av_free(sps); return AVERROR_INVALIDDATA;}代码分析：
1、skip_bits(&h->gb, 2);跳过两个位，表现为GetBitContext.index后移两个位置。
skip_bits只影响GetBitContext.index
2、get_ue_golomb_31计算到的sps_id、chroma_format_idc分别是0、1。
get_ue_golomb_31计算sps_id、chroma_format_idc的值
3、get_ue_golomb读取亮度、色度的位深度都为8。
亮度、色度的位深度
4、解析transform_bypass、log2_max_frame_num和poc_type。因poc_type为0，则log2_max_poc_lsb等于get_ue_golomb(&h->gb) + 4。
5、ref_frame_count由get_ue_golomb_31读取为2。
6、读完gaps_in_frame_num_allowed_flag后，sps索引为47。
读取mb_width前sps的游标
7、宏块宽度。
宏块宽度
8、宏块高度。
宏块高度
9、帧的宽高校对av_image_check_size。
av_image_check_size
根据编码规则计算到的宽高是1920x1088，而MP4中读取的是1920x1080。那么，如何FFmpeg是如何修正SPS里的宽高计算呢？
实际上，SPS还有crop系列字段，由crop表示帧是否被裁剪、crop_left、crop_right、crop_top和crop_bottom表示要裁剪的值得到正确的宽高值。
sps->crop_left = crop_left * step_x;sps->crop_right = crop_right * step_x;sps->crop_top = crop_top * step_y;sps->crop_bottom = crop_bottom * step_y;
crop参数
FFmpeg 3.0对SPS的定义如下。
/** * Sequence parameter set */typedef struct SPS { unsigned int sps_id; int profile_idc; int level_idc; int chroma_format_idc; int transform_bypass; ///< qpprime_y_zero_transform_bypass_flag int log2_max_frame_num; ///< log2_max_frame_num_minus4 + 4 int poc_type; ///< pic_order_cnt_type int log2_max_poc_lsb; ///< log2_max_pic_order_cnt_lsb_minus4 int delta_pic_order_always_zero_flag; int offset_for_non_ref_pic; int offset_for_top_to_bottom_field; int poc_cycle_length; ///< num_ref_frames_in_pic_order_cnt_cycle int ref_frame_count; ///< num_ref_frames int gaps_in_frame_num_allowed_flag; int mb_width; ///< pic_width_in_mbs_minus1 + 1 int mb_height; ///< pic_height_in_map_units_minus1 + 1 int frame_mbs_only_flag; int mb_aff; ///< mb_adaptive_frame_field_flag int direct_8x8_inference_flag; int crop; ///< frame_cropping_flag /* those 4 are already in luma samples */ unsigned int crop_left; ///< frame_cropping_rect_left_offset unsigned int crop_right; ///< frame_cropping_rect_right_offset unsigned int crop_top; ///< frame_cropping_rect_top_offset unsigned int crop_bottom; ///< frame_cropping_rect_bottom_offset int vui_parameters_present_flag; AVRational sar; int video_signal_type_present_flag; int full_range; int colour_description_present_flag; enum AVColorPrimaries color_primaries; enum AVColorTransferCharacteristic color_trc; enum AVColorSpace colorspace; int timing_info_present_flag; uint32_t num_units_in_tick; uint32_t time_scale; int fixed_frame_rate_flag; short offset_for_ref_frame[256]; // FIXME dyn aloc? int bitstream_restriction_flag; int num_reorder_frames; int scaling_matrix_present; uint8_t scaling_matrix4[6][16]; uint8_t scaling_matrix8[6][64]; int nal_hrd_parameters_present_flag; int vcl_hrd_parameters_present_flag; int pic_struct_present_flag; int time_offset_length; int cpb_cnt; ///< See H.264 E.1.2 int initial_cpb_removal_delay_length; ///< initial_cpb_removal_delay_length_minus1 + 1 int cpb_removal_delay_length; ///< cpb_removal_delay_length_minus1 + 1 int dpb_output_delay_length; ///< dpb_output_delay_length_minus1 + 1 int bit_depth_luma; ///< bit_depth_luma_minus8 + 8 int bit_depth_chroma; ///< bit_depth_chroma_minus8 + 8 int residual_color_transform_flag; ///< residual_colour_transform_flag int constraint_set_flags; ///< constraint_set[0-3]_flag int new; ///< flag to keep track if the decoder context needs re-init due to changed SPS uint8_t data[4096]; size_t data_size;} SPS;2、基于ijkplayer的处理
ijkplayer的计算是错误的，这里写出来只作参考。
avcC数据有41字节，详细数据如下。其中，SPS为26字节：27640028 ... C108。
01640028 FFE1001A 27640028 AD00EC07 80227E5C 05B80808 0A000007 D20001D4 C1080100 0428CE3C B0按照H.264编码规则：
- 当前SPS的帧的宽 = (sps_info.pic_width_in_mbs_minus1 + 1) * 16
- 当前SPS的帧的高 = (sps_info.pic_height_in_map_units_minus1 + 1) * 16
然而，通过如下代码计算得到的宽高（1888 x 1920）却不完全等同于源视频的宽高（1920 x 1080）。
int width = (int)(sps_info.pic_width_in_mbs_minus1 + 1) << 4;int height = (int)(sps_info.pic_height_in_map_units_minus1 + 1) << 4;当再往下读unsigned Exp-Golomb code（nal_bs_read_ue(&bs)）且用宽存储当前高（1920）的值，则得到新的高度值1088，显然，这是接近1080这个值的。具体情况是，
sps_info.pic_width_in_mbs_minus1 = 119
sps_info.pic_height_in_map_units_minus1 = 67
那么，对于高度1080的计算是(1080/16.0 - 1) = 67.5 - 1 = 66.5，然而，sps_info.pic_height_in_map_units_minus1类型为uint16_t，显然无法存储66.5，按四舍五入处理，得到67。
解析流程如下：
nal_bitstream bs;sps_info_struct sps_info = {0};nal_bs_init(&bs, sps, sps_size);sps_info.profile_idc = nal_bs_read(&bs, 8);nal_bs_read(&bs, 1); // constraint_set0_flagnal_bs_read(&bs, 1); // constraint_set1_flagnal_bs_read(&bs, 1); // constraint_set2_flagnal_bs_read(&bs, 1); // constraint_set3_flagnal_bs_read(&bs, 4); // reservedsps_info.level_idc = nal_bs_read(&bs, 8);sps_info.sps_id = nal_bs_read_ue(&bs);if (sps_info.profile_idc == 100 || sps_info.profile_idc == 110 || sps_info.profile_idc == 122 || sps_info.profile_idc == 244 || sps_info.profile_idc == 44 || sps_info.profile_idc == 83 || sps_info.profile_idc == 86){ sps_info.chroma_format_idc = nal_bs_read_ue(&bs); if (sps_info.chroma_format_idc == 3) sps_info.separate_colour_plane_flag = nal_bs_read(&bs, 1); sps_info.bit_depth_luma_minus8 = nal_bs_read_ue(&bs); sps_info.bit_depth_chroma_minus8 = nal_bs_read_ue(&bs); sps_info.qpprime_y_zero_transform_bypass_flag = nal_bs_read(&bs, 1); sps_info.seq_scaling_matrix_present_flag = nal_bs_read (&bs, 1); if (sps_info.seq_scaling_matrix_present_flag) { /* TODO: unfinished */ }}sps_info.log2_max_frame_num_minus4 = nal_bs_read_ue(&bs);if (sps_info.log2_max_frame_num_minus4 > 12) { // must be between 0 and 12 // don't early return here - the bits we are using (profile/level/interlaced/ref frames) // might still be valid - let the parser go on and pray. //return;}sps_info.pic_order_cnt_type = nal_bs_read_ue(&bs);if (sps_info.pic_order_cnt_type == 0) { sps_info.log2_max_pic_order_cnt_lsb_minus4 = nal_bs_read_ue(&bs);}else if (sps_info.pic_order_cnt_type == 1) { // TODO: unfinished /* delta_pic_order_always_zero_flag = gst_nal_bs_read (bs, 1); offset_for_non_ref_pic = gst_nal_bs_read_se (bs); offset_for_top_to_bottom_field = gst_nal_bs_read_se (bs); num_ref_frames_in_pic_order_cnt_cycle = gst_nal_bs_read_ue (bs); for( i = 0; i < num_ref_frames_in_pic_order_cnt_cycle; i++ ) offset_for_ref_frame[i] = gst_nal_bs_read_se (bs); */}sps_info.max_num_ref_frames = nal_bs_read_ue(&bs);sps_info.gaps_in_frame_num_value_allowed_flag = nal_bs_read(&bs, 1);sps_info.pic_width_in_mbs_minus1 = nal_bs_read_ue(&bs);sps_info.pic_height_in_map_units_minus1 = nal_bs_read_ue(&bs);// 宽高的计算int width = (int)(sps_info.pic_width_in_mbs_minus1 + 1) << 4;int height = (int)(sps_info.pic_height_in_map_units_minus1 + 1) << 4;ijkplayer的SPS相关操作代码如下所示。
1、定义SPS结体
typedef struct{ uint64_t profile_idc; uint64_t level_idc; uint64_t sps_id; uint64_t chroma_format_idc; uint64_t separate_colour_plane_flag; uint64_t bit_depth_luma_minus8; uint64_t bit_depth_chroma_minus8; uint64_t qpprime_y_zero_transform_bypass_flag; uint64_t seq_scaling_matrix_present_flag; uint64_t log2_max_frame_num_minus4; uint64_t pic_order_cnt_type; uint64_t log2_max_pic_order_cnt_lsb_minus4; uint64_t max_num_ref_frames; uint64_t gaps_in_frame_num_value_allowed_flag; uint64_t pic_width_in_mbs_minus1; uint64_t pic_height_in_map_units_minus1; uint64_t frame_mbs_only_flag; uint64_t mb_adaptive_frame_field_flag; uint64_t direct_8x8_inference_flag; uint64_t frame_cropping_flag; uint64_t frame_crop_left_offset; uint64_t frame_crop_right_offset; uint64_t frame_crop_top_offset; uint64_t frame_crop_bottom_offset;} sps_info_struct;2、NAL位流定义
typedef struct{ const uint8_t *data; const uint8_t *end; int head; uint64_t cache;} nal_bitstream;3、NAL位流操作
static void nal_bs_init(nal_bitstream *bs, const uint8_t *data, size_t size){ bs->data = data; bs->end = data + size; bs->head = 0; // fill with something other than 0 to detect // emulation prevention bytes bs->cache = 0xffffffff;}static uint64_t nal_bs_read(nal_bitstream *bs, int n){ uint64_t res = 0; int shift; if (n == 0) return res; // fill up the cache if we need to while (bs->head < n) { uint8_t a_byte; bool check_three_byte; check_three_byte = true; next_byte: if (bs->data >= bs->end) { // we're at the end, can't produce more than head number of bits n = bs->head; break; } // get the byte, this can be an emulation_prevention_three_byte that we need // to ignore. a_byte = *bs->data++; if (check_three_byte && a_byte == 0x03 && ((bs->cache & 0xffff) == 0)) { // next byte goes unconditionally to the cache, even if it's 0x03 check_three_byte = false; goto next_byte; } // shift bytes in cache, moving the head bits of the cache left bs->cache = (bs->cache << 8) | a_byte; bs->head += 8; } // bring the required bits down and truncate if ((shift = bs->head - n) > 0) res = bs->cache >> shift; else res = bs->cache; // mask out required bits if (n < 32) res &= (1 << n) - 1; bs->head = shift; return res;}static bool nal_bs_eos(nal_bitstream *bs){ return (bs->data >= bs->end) && (bs->head == 0);}// read unsigned Exp-Golomb codestatic int64_t nal_bs_read_ue(nal_bitstream *bs){ int i = 0; while (nal_bs_read(bs, 1) == 0 && !nal_bs_eos(bs) && i < 32) i++; return ((1 << i) - 1 + nal_bs_read(bs, i));}参考：
- IJKPlayer
- FFmpeg 3.0
iOS音视频底层开发与FFmpeg
阅读全文
0 0
- FFmpeg源码调试：解析H.264 SPS(Sequence Parameter Set)中帧的宽高
- THE H.264 SEQUENCE PARAMETER SET
- 一步一步解析H.264码流的NALU(SPS,PSS,IDR)获取宽高和帧率
- H.264中定义的sequence parameter sets
- H.264中定义的sequence parameter sets(zz)
- 【H.264/AVC视频编解码技术详解】 九、序列参数集Sequence Paramater Set(SPS)解析
- H.264-SPS解析
- 如何解析SDP中包含的H.264的SPS和PPS串
- 九、序列参数集Sequence Paramater Set(SPS)解析
- H264中SPS帧分辨率的解析
- H.264 SPS PPS I/P/B帧解析
- h264 sps解析，提取宽高
- RBSP、SODB、EBSP三者的区别和联系 SPS: sequence parameter sets
- H.264的学习sps,pps
- h.264码流解析_一个SPS的nalu及获取视频的分辨率
- H.264码流解析 一个SPS的nalu及获取视频的分辨率
- H.264码流解析 一个SPS的nalu及获取视频的分辨率
- H.264码流解析 一个SPS的nalu及获取视频的分辨率
- 通过request_irq 申请的irq，默认是可以运行在所有online的cpu上
- Mysql存储过程基础
- OpenJudge-2152：Pots
- 几种任务调度的 Java 实现方法与比较
- error LNK1123: 转换到 COFF 期间失败: 文件无效或损坏
- FFmpeg源码调试：解析H.264 SPS(Sequence Parameter Set)中帧的宽高
- 高级Android开发工程师进阶路线
- 构造函数
- Eclipse设置Tomcat
- Android进阶系列
- Spring AOP 理论解析
- centos 制作iso镜像
- Nearest Common Ancestors
- 登录案例
