【FFmpeg编程进阶】（15）FLV 编码器Codec初始化 ff_mpv_encode

【FFmpeg编程进阶】（15）FLV 编码器Codec初始化 ff_mpv_encode_init 代码分析

一、ff_mpv_encode_init()

在前面分析《【FFmpeg编程进阶】（11）avcodec_open2() 函数代码分析 - 打开Codec解码器》时，
我们涉及到了Codec 编码器初始化，由于代码比较长，我们再分一章来分析。

主要目的，还是以 FLV 编码器为例，来看下编码器初始化主要做了啥

# libavcodec\flvenc.c
AVCodec ff_flv_encoder = {.name           = "flv",.long_name      = NULL_IF_CONFIG_SMALL("FLV / Sorenson Spark / Sorenson H.263 (Flash Video)"),.type           = AVMEDIA_TYPE_VIDEO,.id             = AV_CODEC_ID_FLV1,.priv_data_size = sizeof(MpegEncContext),.init           = ff_mpv_encode_init,.encode2        = ff_mpv_encode_picture,.close          = ff_mpv_encode_end,.caps_internal  = FF_CODEC_CAP_INIT_CLEANUP,.pix_fmts       = (const enum AVPixelFormat[]) { AV_PIX_FMT_YUV420P,AV_PIX_FMT_NONE},.priv_class     = &flv_class,
};

一、ff_mpv_encode_init()

初始化解码器上下文 MpegEncContext
结合 avctx->codec_id 和 avctx->pix_fmt 判断编码器是否支持对该pix_fmt格式进行编码
配置 s->chroma_format 参数、s->width、s->height 等一些其他的参数

PS：在编解码核心函数里，看了一个多小时代码，发现其逻辑就目前我的理解来说有点看不懂（慢慢花时间看或许多少也会有收获）
考虑效率及目前的需求，对于目前我这样的新手来说，这些更加高深的编解码知识会有点形而上，
与其花大量时间结合封装格式深专研进去学习，还不如先放手学习其他的基础，
比如先掌握ffmpeg 怎么使用、怎么编程，这些或许在当前阶段更加重要，
对于目前来说，我只需要知道调用这个接口，就会对packet 进行编解码，
至于编解码其详细的原理，等随着音视频学习更深时，基础更好时，再返回来学习，这样可能会更好理解，同时与高效些。
因此，本文加上待更新字样先留个念想，后面学习深入再补上。

# libavcodec\mpegvideo_enc.c
/* init video encoder */
av_cold int ff_mpv_encode_init(AVCodecContext *avctx)
{MpegEncContext *s = avctx->priv_data;AVCPBProperties *cpb_props;// 1. 初始化解码器上下文 MpegEncContextmpv_encode_defaults(s);// 2. 结合 avctx->codec_id 和 avctx->pix_fmt 判断编码器是否支持对该pix_fmt格式进行编码,switch (avctx->codec_id) {case AV_CODEC_ID_MPEG2VIDEO:if (avctx->pix_fmt != AV_PIX_FMT_YUV420P && avctx->pix_fmt != AV_PIX_FMT_YUV422P) {av_log(avctx, AV_LOG_ERROR,  "only YUV420 and YUV422 are supported\n");return AVERROR(EINVAL);}break;case AV_CODEC_ID_MJPEG:case AV_CODEC_ID_AMV:format_supported = 0;/* JPEG color space */if (avctx->pix_fmt == AV_PIX_FMT_YUVJ420P ||avctx->pix_fmt == AV_PIX_FMT_YUVJ422P ||avctx->pix_fmt == AV_PIX_FMT_YUVJ444P ||(avctx->color_range == AVCOL_RANGE_JPEG &&(avctx->pix_fmt == AV_PIX_FMT_YUV420P ||avctx->pix_fmt == AV_PIX_FMT_YUV422P ||avctx->pix_fmt == AV_PIX_FMT_YUV444P)))format_supported = 1;/* MPEG color space */else if (avctx->strict_std_compliance <= FF_COMPLIANCE_UNOFFICIAL &&(avctx->pix_fmt == AV_PIX_FMT_YUV420P ||avctx->pix_fmt == AV_PIX_FMT_YUV422P ||avctx->pix_fmt == AV_PIX_FMT_YUV444P))format_supported = 1;if (!format_supported) {av_log(avctx, AV_LOG_ERROR, "colorspace not supported in jpeg\n");return AVERROR(EINVAL);}break;default:if (avctx->pix_fmt != AV_PIX_FMT_YUV420P) {av_log(avctx, AV_LOG_ERROR, "only YUV420 is supported\n");return AVERROR(EINVAL);}}// 3. 配置s->chroma_format 参数switch (avctx->pix_fmt) {case AV_PIX_FMT_YUVJ444P:case AV_PIX_FMT_YUV444P:s->chroma_format = CHROMA_444;break;case AV_PIX_FMT_YUVJ422P:case AV_PIX_FMT_YUV422P:s->chroma_format = CHROMA_422;break;case AV_PIX_FMT_YUVJ420P:case AV_PIX_FMT_YUV420P:default:s->chroma_format = CHROMA_420;break;avctx->bits_per_raw_sample = av_clip(avctx->bits_per_raw_sample, 0, 8);s->bit_rate = avctx->bit_rate;s->width    = avctx->width;s->height   = avctx->height;if (avctx->gop_size > 600 &&  avctx->strict_std_compliance > FF_COMPLIANCE_EXPERIMENTAL) {av_log(avctx, AV_LOG_WARNING, "keyframe interval too large!, reducing it from %d to %d\n", avctx->gop_size, 600);avctx->gop_size = 600;}s->gop_size     = avctx->gop_size;s->avctx        = avctx;if (avctx->max_b_frames > MAX_B_FRAMES) {av_log(avctx, AV_LOG_ERROR, "Too many B-frames requested, maximum ""is %d.\n", MAX_B_FRAMES);avctx->max_b_frames = MAX_B_FRAMES;}s->max_b_frames = avctx->max_b_frames;s->codec_id     = avctx->codec->id;s->strict_std_compliance = avctx->strict_std_compliance;s->quarter_sample     = (avctx->flags & AV_CODEC_FLAG_QPEL) != 0;s->rtp_mode           = !!s->rtp_payload_size;s->intra_dc_precision = avctx->intra_dc_precision;// workaround some differences between how applications specify dc precisionif (s->intra_dc_precision < 0) {s->intra_dc_precision += 8;} else if (s->intra_dc_precision >= 8)s->intra_dc_precision -= 8;if (avctx->codec_id == AV_CODEC_ID_AMV || (avctx->active_thread_type & FF_THREAD_SLICE))s->huffman = 0;s->user_specified_pts = AV_NOPTS_VALUE;if (s->gop_size <= 1) {s->intra_only = 1;s->gop_size   = 12;} else {s->intra_only = 0;}/* Fixed QSCALE */s->fixed_qscale = !!(avctx->flags & AV_CODEC_FLAG_QSCALE);s->adaptive_quant = (avctx->lumi_masking ||avctx->dark_masking ||avctx->temporal_cplx_masking ||avctx->spatial_cplx_masking  ||avctx->p_masking      ||s->border_masking ||(s->mpv_flags & FF_MPV_FLAG_QP_RD)) &&!s->fixed_qscale;s->loop_filter = !!(avctx->flags & AV_CODEC_FLAG_LOOP_FILTER);if (avctx->rc_max_rate && !avctx->rc_buffer_size) {switch(avctx->codec_id) {case AV_CODEC_ID_MPEG1VIDEO:case AV_CODEC_ID_MPEG2VIDEO:avctx->rc_buffer_size = FFMAX(avctx->rc_max_rate, 15000000) * 112LL / 15000000 * 16384;break;case AV_CODEC_ID_MPEG4:case AV_CODEC_ID_MSMPEG4V1:case AV_CODEC_ID_MSMPEG4V2:case AV_CODEC_ID_MSMPEG4V3:if       (avctx->rc_max_rate >= 15000000) {avctx->rc_buffer_size = 320 + (avctx->rc_max_rate - 15000000LL) * (760-320) / (38400000 - 15000000);} else if(avctx->rc_max_rate >=  2000000) {avctx->rc_buffer_size =  80 + (avctx->rc_max_rate -  2000000LL) * (320- 80) / (15000000 -  2000000);} else if(avctx->rc_max_rate >=   384000) {avctx->rc_buffer_size =  40 + (avctx->rc_max_rate -   384000LL) * ( 80- 40) / ( 2000000 -   384000);} elseavctx->rc_buffer_size = 40;avctx->rc_buffer_size *= 16384;break;}if (avctx->rc_buffer_size) {av_log(avctx, AV_LOG_INFO, "Automatically choosing VBV buffer size of %d kbyte\n", avctx->rc_buffer_size/8192);}}if ((s->codec_id == AV_CODEC_ID_MPEG4 ||s->codec_id == AV_CODEC_ID_H263  ||s->codec_id == AV_CODEC_ID_H263P) &&(avctx->sample_aspect_ratio.num > 255 ||avctx->sample_aspect_ratio.den > 255)) {av_log(avctx, AV_LOG_WARNING, "Invalid pixel aspect ratio %i/%i, limit is 255/255 reducing\n",avctx->sample_aspect_ratio.num, avctx->sample_aspect_ratio.den);av_reduce(&avctx->sample_aspect_ratio.num, &avctx->sample_aspect_ratio.den,avctx->sample_aspect_ratio.num,  avctx->sample_aspect_ratio.den, 255);}if (s->mpeg_quant || s->codec_id == AV_CODEC_ID_MPEG1VIDEO || s->codec_id == AV_CODEC_ID_MPEG2VIDEO || s->codec_id == AV_CODEC_ID_MJPEG || s->codec_id==AV_CODEC_ID_AMV) {// (a + x * 3 / 8) / xs->intra_quant_bias = 3 << (QUANT_BIAS_SHIFT - 3);s->inter_quant_bias = 0;} else {s->intra_quant_bias = 0;// (a - x / 4) / xs->inter_quant_bias = -(1 << (QUANT_BIAS_SHIFT - 2));}av_log(avctx, AV_LOG_DEBUG, "intra_quant_bias = %d inter_quant_bias = %d\n",s->intra_quant_bias,s->inter_quant_bias);s->time_increment_bits = av_log2(avctx->time_base.den - 1) + 1;switch (avctx->codec->id) {case AV_CODEC_ID_MPEG1VIDEO:s->out_format = FMT_MPEG1;s->low_delay  = !!(avctx->flags & AV_CODEC_FLAG_LOW_DELAY);avctx->delay  = s->low_delay ? 0 : (s->max_b_frames + 1);break;case AV_CODEC_ID_MPEG2VIDEO:s->out_format = FMT_MPEG1;s->low_delay  = !!(avctx->flags & AV_CODEC_FLAG_LOW_DELAY);avctx->delay  = s->low_delay ? 0 : (s->max_b_frames + 1);s->rtp_mode   = 1;break;case AV_CODEC_ID_MJPEG:case AV_CODEC_ID_AMV:s->out_format = FMT_MJPEG;s->intra_only = 1; /* force intra only for jpeg */ret = ff_mjpeg_encode_init(s);avctx->delay = 0;s->low_delay = 1;break;case AV_CODEC_ID_H261:if (ff_h261_get_picture_format(s->width, s->height) < 0) {av_log(avctx, AV_LOG_ERROR, "The specified picture size of %dx%d is not valid for the ""H.261 codec.\nValid sizes are 176x144, 352x288\n",s->width, s->height);return AVERROR(EINVAL);}s->out_format = FMT_H261;avctx->delay  = 0;s->low_delay  = 1;s->rtp_mode   = 0; /* Sliced encoding not supported */break;case AV_CODEC_ID_H263:if (!CONFIG_H263_ENCODER)return AVERROR_ENCODER_NOT_FOUND;if (ff_match_2uint16(ff_h263_format, FF_ARRAY_ELEMS(ff_h263_format),s->width, s->height) == 8) {av_log(avctx, AV_LOG_ERROR,"The specified picture size of %dx%d is not valid for ""the H.263 codec.\nValid sizes are 128x96, 176x144, ""352x288, 704x576, and 1408x1152. ""Try H.263+.\n", s->width, s->height);return AVERROR(EINVAL);}s->out_format = FMT_H263;avctx->delay  = 0;s->low_delay  = 1;break;case AV_CODEC_ID_H263P:s->out_format = FMT_H263;s->h263_plus  = 1;/* Fx */s->h263_aic        = (avctx->flags & AV_CODEC_FLAG_AC_PRED) ? 1 : 0;s->modified_quant  = s->h263_aic;s->loop_filter     = (avctx->flags & AV_CODEC_FLAG_LOOP_FILTER) ? 1 : 0;s->unrestricted_mv = s->obmc || s->loop_filter || s->umvplus;/* /Fx *//* These are just to be sure */avctx->delay = 0;s->low_delay = 1;break;case AV_CODEC_ID_FLV1:s->out_format      = FMT_H263;s->h263_flv        = 2; /* format = 1; 11-bit codes */s->unrestricted_mv = 1;s->rtp_mode  = 0; /* don't allow GOB */avctx->delay = 0;s->low_delay = 1;break;case AV_CODEC_ID_RV10:s->out_format = FMT_H263;avctx->delay  = 0;s->low_delay  = 1;break;case AV_CODEC_ID_RV20:s->out_format      = FMT_H263;avctx->delay       = 0;s->low_delay       = 1;s->modified_quant  = 1;s->h263_aic        = 1;s->h263_plus       = 1;s->loop_filter     = 1;s->unrestricted_mv = 0;break;case AV_CODEC_ID_MPEG4:s->out_format      = FMT_H263;s->h263_pred       = 1;s->unrestricted_mv = 1;s->low_delay       = s->max_b_frames ? 0 : 1;avctx->delay       = s->low_delay ? 0 : (s->max_b_frames + 1);break;case AV_CODEC_ID_MSMPEG4V2:s->out_format      = FMT_H263;s->h263_pred       = 1;s->unrestricted_mv = 1;s->msmpeg4_version = 2;avctx->delay       = 0;s->low_delay       = 1;break;case AV_CODEC_ID_MSMPEG4V3:s->out_format        = FMT_H263;s->h263_pred         = 1;s->unrestricted_mv   = 1;s->msmpeg4_version   = 3;s->flipflop_rounding = 1;avctx->delay         = 0;s->low_delay         = 1;break;case AV_CODEC_ID_WMV1:s->out_format        = FMT_H263;s->h263_pred         = 1;s->unrestricted_mv   = 1;s->msmpeg4_version   = 4;s->flipflop_rounding = 1;avctx->delay         = 0;s->low_delay         = 1;break;case AV_CODEC_IDavctx->has_b_frames = !s->low_delay;s->encoding = 1;s->progressive_frame    =s->progressive_sequence = !(avctx->flags & (AV_CODEC_FLAG_INTERLACED_DCT |AV_CODEC_FLAG_INTERLACED_ME) ||s->alternate_scan);/* init */ff_mpv_idct_init(s);if ((ret = ff_mpv_common_init(s)) < 0)return ret;ff_fdctdsp_init(&s->fdsp, avctx);ff_me_cmp_init(&s->mecc, avctx);ff_mpegvideoencdsp_init(&s->mpvencdsp, avctx);ff_pixblockdsp_init(&s->pdsp, avctx);ff_qpeldsp_init(&s->qdsp);if (s->msmpeg4_version) {int ac_stats_size = 2 * 2 * (MAX_LEVEL + 1) *  (MAX_RUN + 1) * 2 * sizeof(int);if (!(s->ac_stats = av_mallocz(ac_stats_size)))return AVERROR(ENOMEM);}if (!(avctx->stats_out = av_mallocz(256))               ||!FF_ALLOCZ_TYPED_ARRAY(s->q_intra_matrix,          32) ||!FF_ALLOCZ_TYPED_ARRAY(s->q_chroma_intra_matrix,   32) ||!FF_ALLOCZ_TYPED_ARRAY(s->q_inter_matrix,          32) ||!FF_ALLOCZ_TYPED_ARRAY(s->q_intra_matrix16,        32) ||!FF_ALLOCZ_TYPED_ARRAY(s->q_chroma_intra_matrix16, 32) ||!FF_ALLOCZ_TYPED_ARRAY(s->q_inter_matrix16,        32) ||!FF_ALLOCZ_TYPED_ARRAY(s->input_picture,           MAX_PICTURE_COUNT) ||!FF_ALLOCZ_TYPED_ARRAY(s->reordered_input_picture, MAX_PICTURE_COUNT))return AVERROR(ENOMEM);if (s->noise_reduction) {if (!FF_ALLOCZ_TYPED_ARRAY(s->dct_offset, 2))return AVERROR(ENOMEM);}ff_dct_encode_init(s);if ((CONFIG_H263P_ENCODER || CONFIG_RV20_ENCODER) && s->modified_quant)s->chroma_qscale_table = ff_h263_chroma_qscale_table;if (s->slice_context_count > 1) {s->rtp_mode = 1;if (avctx->codec_id == AV_CODEC_ID_H263P)s->h263_slice_structured = 1;}s->quant_precision = 5;#if FF_API_PRIVATE_OPT
FF_DISABLE_DEPRECATION_WARNINGSif (avctx->frame_skip_threshold)s->frame_skip_threshold = avctx->frame_skip_threshold;if (avctx->frame_skip_factor)s->frame_skip_factor = avctx->frame_skip_factor;if (avctx->frame_skip_exp)s->frame_skip_exp = avctx->frame_skip_exp;if (avctx->frame_skip_cmp != FF_CMP_DCTMAX)s->frame_skip_cmp = avctx->frame_skip_cmp;
FF_ENABLE_DEPRECATION_WARNINGS
#endifff_set_cmp(&s->mecc, s->mecc.ildct_cmp,      avctx->ildct_cmp);ff_set_cmp(&s->mecc, s->mecc.frame_skip_cmp, s->frame_skip_cmp);if (CONFIG_H261_ENCODER && s->out_format == FMT_H261)ff_h261_encode_init(s);if (CONFIG_H263_ENCODER && s->out_format == FMT_H263)ff_h263_encode_init(s);if (CONFIG_MSMPEG4_ENCODER && s->msmpeg4_version)if ((ret = ff_msmpeg4_encode_init(s)) < 0)return ret;if ((CONFIG_MPEG1VIDEO_ENCODER || CONFIG_MPEG2VIDEO_ENCODER)&& s->out_format == FMT_MPEG1)ff_mpeg1_encode_init(s);/* init q matrix */for (i = 0; i < 64; i++) {int j = s->idsp.idct_permutation[i];if (CONFIG_MPEG4_ENCODER && s->codec_id == AV_CODEC_ID_MPEG4 &&s->mpeg_quant) {s->intra_matrix[j] = ff_mpeg4_default_intra_matrix[i];s->inter_matrix[j] = ff_mpeg4_default_non_intra_matrix[i];} else if (s->out_format == FMT_H263 || s->out_format == FMT_H261) {s->intra_matrix[j] =s->inter_matrix[j] = ff_mpeg1_default_non_intra_matrix[i];} else {/* MPEG-1/2 */s->chroma_intra_matrix[j] =s->intra_matrix[j] = ff_mpeg1_default_intra_matrix[i];s->inter_matrix[j] = ff_mpeg1_default_non_intra_matrix[i];}if (avctx->intra_matrix)s->intra_matrix[j] = avctx->intra_matrix[i];if (avctx->inter_matrix)s->inter_matrix[j] = avctx->inter_matrix[i];}/* precompute matrix *//* for mjpeg, we do include qscale in the matrix */if (s->out_format != FMT_MJPEG) {ff_convert_matrix(s, s->q_intra_matrix, s->q_intra_matrix16,s->intra_matrix, s->intra_quant_bias, avctx->qmin,31, 1);ff_convert_matrix(s, s->q_inter_matrix, s->q_inter_matrix16,s->inter_matrix, s->inter_quant_bias, avctx->qmin,31, 0);}if ((ret = ff_rate_control_init(s)) < 0)return ret;#if FF_API_PRIVATE_OPTFF_DISABLE_DEPRECATION_WARNINGSif (avctx->brd_scale)s->brd_scale = avctx->brd_scale;if (avctx->prediction_method)s->pred = avctx->prediction_method + 1;FF_ENABLE_DEPRECATION_WARNINGS
#endifif (s->b_frame_strategy == 2) {for (i = 0; i < s->max_b_frames + 2; i++) {s->tmp_frames[i] = av_frame_alloc();if (!s->tmp_frames[i])return AVERROR(ENOMEM);s->tmp_frames[i]->format = AV_PIX_FMT_YUV420P;s->tmp_frames[i]->width  = s->width  >> s->brd_scale;s->tmp_frames[i]->height = s->height >> s->brd_scale;ret = av_frame_get_buffer(s->tmp_frames[i], 0);if (ret < 0)return ret;}}cpb_props = ff_add_cpb_side_data(avctx);if (!cpb_props)return AVERROR(ENOMEM);cpb_props->max_bitrate = avctx->rc_max_rate;cpb_props->min_bitrate = avctx->rc_min_rate;cpb_props->avg_bitrate = avctx->bit_rate;cpb_props->buffer_size = avctx->rc_buffer_size;return 0;
}

【FFmpeg编程进阶】（15）FLV 编码器Codec初始化 ff_mpv_encode_init() 代码分析 -- 待更新相关推荐

U-boot之flash初始化完全代码分析
一代码分析 1.Board->dave->flash.c #include <common.h> #include <asm/hardware.h> #inc ...
Struts2初始化过程代码分析
根据web.xml的配置调用FilterDispatcher.init(FilterConfig filterConfig) 1. 创建org.apache.struts2.Dispatcher,并 ...
轻松掌握FFmpeg编程：从架构到实践
轻松掌握FFmpeg编程:从架构到实践 (Master FFmpeg Programming with Ease: From Architecture to Practice 引言 (Introduc ...
基于Transformer的文本情感分析编程实践（Encoder编码器-Decoder解码器框架 + Attention注意力机制 + Positional Encoding位置编码）
日萌社人工智能AI:Keras PyTorch MXNet TensorFlow PaddlePaddle 深度学习实战(不定时更新) Encoder编码器-Decoder解码器框架 + Atten ...
Python开发系列课程(11) - 面向对象编程进阶
面向对象编程进阶在前面的章节我们已经了解了面向对象的入门知识,知道了如何定义类,如何创建对象以及如何给对象发消息.为了能够更好的使用面向对象编程思想进行程序开发,我们还需要对Python中的面向对象 ...
shell编程进阶技能详细介绍
Shell脚本编程进阶一.循环 1.for循环 2.while循环 3.until循环 4.循环控制语句continu 5.循环控制语句break 6.循环控制shift命令 7.while特殊用法 ...
基于Seq2Seq的中文聊天机器人编程实践（Encoder编码器-Decoder解码器框架 + Attention注意力机制）
日萌社人工智能AI:Keras PyTorch MXNet TensorFlow PaddlePaddle 深度学习实战(不定时更新) Encoder编码器-Decoder解码器框架 + Atten ...
MOOS-ivp 实验五 MOOS编程进阶（3）
MOOS-ivp 实验五 MOOS编程进阶(3) 经过近日的学习与摸索,我来重新完善以下实验五的相关内容,上次做到三分之二的内容放弃了,主要原因还是因为C++功底不够深厚,需要更多的学习和积累.经过我 ...
MOOS-ivp 实验五 MOOS编程进阶（2）
MOOS-ivp 实验五 MOOS编程进阶(2) 今天继续我的实验,感觉每个实验都要被卡住,这种感觉真的好难受,但是如果把问题成功的解决掉,又会给人以非常大的成就感.今天写这篇博客,希望我可以相对顺利 ...

【FFmpeg编程进阶】（15）FLV 编码器Codec初始化 ff_mpv_encode_init() 代码分析 -- 待更新

【FFmpeg编程进阶】（15）FLV 编码器Codec初始化 ff_mpv_encode_init 代码分析

一、ff_mpv_encode_init()

【FFmpeg编程进阶】（15）FLV 编码器Codec初始化 ff_mpv_encode_init() 代码分析 -- 待更新相关推荐

最新文章

热门文章