【FFmpeg4.1.4 编码】h265编码

FFmpeg

1、编码流程
2、编码

1、编码流程

1、初始化AVFormatContext：avformat_alloc_output_context2()，包含有输出码流(AVStream)和解复用器(AVInputFormat)。
2、打开输出文件：avio_open()。
3、初始化AVCodecContext：avcodec_alloc_context3()，包含编码参数信息。
4、创建视频码流：avformat_new_stream()，该函数生成一个空AVstream 该结构存放编码后的视频码流。视频码流被拆分为AVPacket新式保存在AVStream中。
5、拷贝编码参数信息：avcodec_parameters_from_context()，从AVCodecContext到输出流中。
6、写头信息：avformat_write_header()，将封装格式的信息写入文件头部位置。
7、查找编码器：avcodec_find_encoder()。
8、设置编码器信息：AVCodecContext
码率：bit_rate
图像格式：pix_fmt
分辨率：width、height
帧率：framerate、time_base
GOP大小：gop_size
B帧：max_b_frames
额外设置一些参数(如 h265 要设置qmax、qmin、qcompress参数才能正常使用h264编码)
9、打开编码器：avcodec_open2()，根据前一步设置的编码器参数信息，来查找初始化一个编码器，并将其打开。
10、分配AVPacket和AVFrame：av_packet_alloc()和av_frame_alloc()
11、编码：avcodec_send_frame()和avcodec_receive_packet()。
12、写入输出文件：av_interleaved_write_frame()。

2、编码

/** Copyright (c) 2001 Fabrice Bellard** Permission is hereby granted, free of charge, to any person obtaining a copy* of this software and associated documentation files (the "Software"), to deal* in the Software without restriction, including without limitation the rights* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell* copies of the Software, and to permit persons to whom the Software is* furnished to do so, subject to the following conditions:** The above copyright notice and this permission notice shall be included in* all copies or substantial portions of the Software.** THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN* THE SOFTWARE.*//*** @file* video encoding with libavcodec API example** @example encode_video.c*/#include <stdio.h>
#include <stdlib.h>
#include <string.h>#ifdef __cplusplus
extern "C" {#endif // __cplusplus#include <libavcodec/avcodec.h>
#include <libavutil/opt.h>
#include <libavutil/imgutils.h>#ifdef __cplusplus
}
#endif // __cplusplusstatic void encode(AVCodecContext *enc_ctx, AVFrame *frame, AVPacket *pkt,FILE *outfile)
{int ret;/* send the frame to the encoder */if (frame)printf("Send frame %3"PRId64"\n", frame->pts);ret = avcodec_send_frame(enc_ctx, frame);if (ret < 0) {fprintf(stderr, "Error sending a frame for encoding\n");exit(1);}while (ret >= 0) {ret = avcodec_receive_packet(enc_ctx, pkt);if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)return;else if (ret < 0) {fprintf(stderr, "Error during encoding\n");exit(1);}printf("Write packet %3"PRId64" (size=%5d)\n", pkt->pts, pkt->size);fwrite(pkt->data, 1, pkt->size, outfile);av_packet_unref(pkt);}
}int main(int argc, char **argv)
{const char *filename, *codec_name;const AVCodec *codec;AVCodecContext *c= NULL;AVCodecID codec_id = AV_CODEC_ID_HEVC;int i, ret, x, y;FILE *f;AVFrame *frame;AVPacket *pkt;uint8_t endcode[] = { 0, 0, 1, 0xb7 };if (argc <= 2) {fprintf(stderr, "Usage: %s <output file> <codec name>\n", argv[0]);exit(0);}filename = argv[1];codec_name = argv[2];/* find the mpeg1video encoder */codec = avcodec_find_encoder(codec_id);if (!codec) {fprintf(stderr, "Codec '%s' not found\n", codec_name);exit(1);}c = avcodec_alloc_context3(codec);if (!c) {fprintf(stderr, "Could not allocate video codec context\n");exit(1);}pkt = av_packet_alloc();if (!pkt)exit(1);/* put sample parameters */c->bit_rate = 400000;/* resolution must be a multiple of two */c->width = 352;c->height = 288;/* frames per second */c->time_base = (AVRational){1, 25};c->framerate = (AVRational){25, 1};/* emit one intra frame every ten frames* check frame pict_type before passing frame* to encoder, if frame->pict_type is AV_PICTURE_TYPE_I* then gop_size is ignored and the output of encoder* will always be I frame irrespective to gop_size*/c->gop_size = 10;c->max_b_frames = 1;c->pix_fmt = AV_PIX_FMT_YUV420P;if (codec->id == AV_CODEC_ID_H264)av_opt_set(c->priv_data, "preset", "slow", 0);/* open it */ret = avcodec_open2(c, codec, NULL);if (ret < 0) {fprintf(stderr, "Could not open codec: %s\n", av_err2str(ret));exit(1);}f = fopen(filename, "wb");if (!f) {fprintf(stderr, "Could not open %s\n", filename);exit(1);}frame = av_frame_alloc();if (!frame) {fprintf(stderr, "Could not allocate video frame\n");exit(1);}frame->format = c->pix_fmt;frame->width  = c->width;frame->height = c->height;ret = av_frame_get_buffer(frame, 32);if (ret < 0) {fprintf(stderr, "Could not allocate the video frame data\n");exit(1);}/* encode 1 second of video */for (i = 0; i < 25; i++) {fflush(stdout);/* make sure the frame data is writable */ret = av_frame_make_writable(frame);if (ret < 0)exit(1);/* prepare a dummy image *//* Y */for (y = 0; y < c->height; y++) {for (x = 0; x < c->width; x++) {frame->data[0][y * frame->linesize[0] + x] = x + y + i * 3;}}/* Cb and Cr */for (y = 0; y < c->height/2; y++) {for (x = 0; x < c->width/2; x++) {frame->data[1][y * frame->linesize[1] + x] = 128 + y + i * 2;frame->data[2][y * frame->linesize[2] + x] = 64 + x + i * 5;}}frame->pts = i;/* encode the image */encode(c, frame, pkt, f);}/* flush the encoder */encode(c, NULL, pkt, f);/* add sequence end code to have a real MPEG file */fwrite(endcode, 1, sizeof(endcode), f);fclose(f);avcodec_free_context(&c);av_frame_free(&frame);av_packet_free(&pkt);return 0;
}