Windows下ffmpeg调用测试（YUV420P编码）
1下载静态库和动态库
如果你是动态加载，可以直接使用动态库（dlopen等）；否则就才用动态+ 静态的方式（动态库的静态加载方式）；或者直接将静态库编译到你的执行程序（纯静态组件使用）；
https://www.gyan.dev/ffmpeg/builds/#libraries
添加组件
vs2022: 属性->c/c++->附加包含目录;将头文件目录添加进去
属性->链接器->附加库目录，添加静态库路径；然后运行的时候记得吧dll放到EXE目录
2 .YUV420P 编码264
选择YUV420P（YV12）是因为，这个数据我可以通过FFmpeg命令行解析文件得到，用来测试，而且planner格式的数据Y,V,U是连续且单独放置的，不会存在UV交叉；YUV一帧的数据量就是width*heigt*1.5
随便找一个MP4录像，用FFmpeg命令行得到YUV数据，用来测试，ffmpeg -i input.mp4 -vf "format=yuv420p" output.yuv；如果你本身就有YUV测试数据，或者数据来源于实时的录像，截屏等等，就可以直接用；
下边的是FFmpeg提供的测试demo的源码，是自己生成的YUV，然后设置编码参数，输出264；我后边会根据这个demo进行一点点改动；不过最主要还是使用这个demo
/*
* 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 libavcodec encoding video API usage example
* @example encode_video.c
*
* Generate synthetic video data and encode it to an output file.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <libavcodec/avcodec.h>
#include <libavutil/opt.h>
#include <libavutil/imgutils.h>
static 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;
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_by_name(codec_name);
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, 0);
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.
On the first round, the frame is fresh from av_frame_get_buffer()
and therefore we know it is writable.
But on the next rounds, encode() will have called
avcodec_send_frame(), and the codec may have kept a reference to
the frame in its internal structures, that makes the frame
unwritable.
av_frame_make_writable() checks that and allocates a new buffer
for the frame only if necessary.
*/
ret = av_frame_make_writable(frame);
if (ret < 0)
exit(1);
/* Prepare a dummy image.
In real code, this is where you would have your own logic for
filling the frame. FFmpeg does not care what you put in the
frame.
*/
/* 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.
It makes only sense because this tiny examples writes packets
directly. This is called "elementary stream" and only works for some
codecs. To create a valid file, you usually need to write packets
into a proper file format or protocol; see mux.c.
*/
if (codec->id == AV_CODEC_ID_MPEG1VIDEO || codec->id == AV_CODEC_ID_MPEG2VIDEO)
fwrite(endcode, 1, sizeof(endcode), f);
fclose(f);
avcodec_free_context(&c);
av_frame_free(&frame);
av_packet_free(&pkt);
return 0;
}
函数介绍
1 查找编码器；还可以使用AVcodec_find_encoder(condec_ID)
const AVCodec* codec = avcodec_find_encoder_by_name(codec_name);//codec_name = "libx264";
函数返回的AVCodec结构体指针，内部包含编码ID，支持的帧率，支持的像素格式，音频采样率，声道，编码档次等
1 /** 2 * AVCodec. 3 */ 4 typedef struct AVCodec { 5 /** 6 * Name of the codec implementation. 7 * The name is globally unique among encoders and among decoders (but an 8 * encoder and a decoder can share the same name). 9 * This is the primary way to find a codec from the user perspective. 10 */ 11 const char *name; 12 /** 13 * Descriptive name for the codec, meant to be more human readable than name. 14 * You should use the NULL_IF_CONFIG_SMALL() macro to define it. 15 */ 16 const char *long_name; 17 enum AVMediaType type; 18 enum AVCodecID id; 19 /** 20 * Codec capabilities. 21 * see AV_CODEC_CAP_* 22 */ 23 int capabilities; 24 uint8_t max_lowres; ///< maximum value for lowres supported by the decoder 25 const AVRational *supported_framerates; ///< array of supported framerates, or NULL if any, array is terminated by {0,0} 26 const enum AVPixelFormat *pix_fmts; ///< array of supported pixel formats, or NULL if unknown, array is terminated by -1 27 const int *supported_samplerates; ///< array of supported audio samplerates, or NULL if unknown, array is terminated by 0 28 const enum AVSampleFormat *sample_fmts; ///< array of supported sample formats, or NULL if unknown, array is terminated by -1 29 #if FF_API_OLD_CHANNEL_LAYOUT 30 /** 31 * @deprecated use ch_layouts instead 32 */ 33 attribute_deprecated 34 const uint64_t *channel_layouts; ///< array of support channel layouts, or NULL if unknown. array is terminated by 0 35 #endif 36 const AVClass *priv_class; ///< AVClass for the private context 37 const AVProfile *profiles; ///< array of recognized profiles, or NULL if unknown, array is terminated by {FF_PROFILE_UNKNOWN} 38 39 /** 40 * Group name of the codec implementation. 41 * This is a short symbolic name of the wrapper backing this codec. A 42 * wrapper uses some kind of external implementation for the codec, such 43 * as an external library, or a codec implementation provided by the OS or 44 * the hardware. 45 * If this field is NULL, this is a builtin, libavcodec native codec. 46 * If non-NULL, this will be the suffix in AVCodec.name in most cases 47 * (usually AVCodec.name will be of the form "<codec_name>_<wrapper_name>"). 48 */ 49 const char *wrapper_name; 50 51 /** 52 * Array of supported channel layouts, terminated with a zeroed layout. 53 */ 54 const AVChannelLayout *ch_layouts; 55 } AVCodec;
2 分配/创建 编码器上下文
作用就是创建上下文，设置编码参数；创建一个上下文之后，就可以设置一些参数了，这个参数会作用到编码器；
AVCodecContext* c = NULL; c = avcodec_alloc_context3(codec);
/* put sample parameters */ c->bit_rate = 400000; //输出码率4M /* resolution must be a multiple of two */ c->width = 1920; //输入的图像宽度，与YUV数据量对应上 c->height = 1080;//输入图像的高 /* frames per second */ c->time_base.num = 1; c->time_base.den = 25; c->framerate.num = 25; //25 FPS c->framerate.den = 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; //GOP 大小是10帧 c->max_b_frames = 1;//每个I、P帧之间最多插入1个B帧 c->pix_fmt = AV_PIX_FMT_YUV420P;//YV 12 planner格式；YVU连续且不存在UV交叉的一种存储格式
3 初始化编码器上下文，在上边第二步创建，设置参数后，初始化上下文，打开编码器
avcodec_open2(c, codec, NULL[用户自定义编码选项]);//const AVCodec* codec; AVCodecContext* c = NULL;
4 创建frame，和package结构 用于承载数据
未压缩的图像放在frame结构体里，编码后的数据放到package结构体里；并不是所有的开源代码里frame存的都是未压缩数据，这个依照具体情况而定；在本博客的测试用例中frame存的是未压缩的YUV数据；有些地方frame存的是264,265数据，使用场景不同，意义也不一样
ffmpeg中的data存储未压缩数据，可以存储平铺模式planer，也可以存(交叉存储packed)的数据；(存储方式的差异主要体现在音频，如左右声道交叉存储，还是每个声道单独存储)
frame = av_frame_alloc();
pkt = av_packet_alloc();
frame = av_frame_alloc(); if (!frame) { fprintf(stderr, "Could not allocate video frame\n"); exit(1); } frame->format = c->pix_fmt;//颜色格式，可设置YUV420P frame->width = c->width; frame->height = c->height; ret = av_frame_get_buffer(frame, 0);//后边每次复用buffer来装YUV之前，要先保证buffer没被占用，是可写的，av_frame_make_writable if (ret < 0) { fprintf(stderr, "Could not allocate the video frame data\n"); exit(1); }
5 读取YUV数据，放到frame的data里边，编码；注意这里的输入输出缓冲都是复用的，是一个 读-编码-输出，串行逻辑
int res_len = fread(buffer,len ,1,fpin); if (res_len > 0) { frame->data[0] = buffer;//Y分量 frame->data[2] =buffer + frame->width * frame->height;//V分量 frame->data[1] = buffer + frame->width * frame->height * 5 / 4;//U 分量 frame->pts += 1;//显示时间戳
//frame 还可以设置该帧要不要编码成关键帧，帧类型等；
/* encode the image */ encode(c, frame, pkt, frle_out_ptr); }
5 AVpackage用来保存编码后的数据，如果H264编码，那这里就是H264的NAL数据，也就是ES流，内部还会保存当前帧的PTS，DTS
编码函数的实现是，送YUV数据，获取Package: avcodec_send_frame(enc_ctx, frame); avcodec_receive_packet(enc_ctx, pkt);
将数据写到文件，解除对package的引用：fwrite(pkt->data, 1, pkt->size, outfile); av_packet_unref(pkt);
typedef struct AVPacket { /** * A reference to the reference-counted buffer where the packet data is * stored. * May be NULL, then the packet data is not reference-counted. */ AVBufferRef *buf; /** * Presentation timestamp in AVStream->time_base units; the time at which * the decompressed packet will be presented to the user. * Can be AV_NOPTS_VALUE if it is not stored in the file. * pts MUST be larger or equal to dts as presentation cannot happen before * decompression, unless one wants to view hex dumps. Some formats misuse * the terms dts and pts/cts to mean something different. Such timestamps * must be converted to true pts/dts before they are stored in AVPacket. */ int64_t pts; /** * Decompression timestamp in AVStream->time_base units; the time at which * the packet is decompressed. * Can be AV_NOPTS_VALUE if it is not stored in the file. */ int64_t dts; uint8_t *data; int size; int stream_index; /** * A combination of AV_PKT_FLAG values */ int flags; /** * Additional packet data that can be provided by the container. * Packet can contain several types of side information. */ AVPacketSideData *side_data; int side_data_elems; /** * Duration of this packet in AVStream->time_base units, 0 if unknown. * Equals next_pts - this_pts in presentation order. */ int64_t duration; int64_t pos; ///< byte position in stream, -1 if unknown /** * for some private data of the user */ void *opaque; /** * AVBufferRef for free use by the API user. FFmpeg will never check the * contents of the buffer ref. FFmpeg calls av_buffer_unref() on it when * the packet is unreferenced. av_packet_copy_props() calls create a new * reference with av_buffer_ref() for the target packet's opaque_ref field. * * This is unrelated to the opaque field, although it serves a similar * purpose. */ AVBufferRef *opaque_ref; /** * Time base of the packet's timestamps. * In the future, this field may be set on packets output by encoders or * demuxers, but its value will be by default ignored on input to decoders * or muxers. */ AVRational time_base; } AVPacket;
6 编码完之后要再次调用下空数据的编码。以防有数据在编码器中未刷新出来
/* flush the encoder */
encode(c, NULL, pkt, fout);
并在编码输出文件结尾添加上mpeg的结束标记 uint8_t endcode[] = { 0, 0, 1, 0xb7 };
7 最后就是释放上下文，释放frame，package，关闭文件
avcodec_free_context(&c);
av_frame_free(&frame);
av_packet_free(&pkt);
下边提供一个真实可以编码的例子：（visual studio 2022）
#include <stdio.h> #include <stdlib.h> #include <string.h> extern "C" { #include <libavcodec/avcodec.h> #include <libavutil/opt.h> #include <libavutil/imgutils.h> char av_error[AV_ERROR_MAX_STRING_SIZE] = { 0 }; #define av_err2str(errnum) av_make_error_string(av_error, AV_ERROR_MAX_STRING_SIZE, errnum) static void encode(AVCodecContext* enc_ctx, AVFrame* frame, AVPacket* pkt, FILE* outfile) { int ret; /* send the frame to the encoder */ if (frame) printf("Send frame %3ld\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 %3ld (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,* filename_in; // const AVCodec* codec; AVCodecContext* c = NULL; int i, ret, x, y; FILE* f; AVFrame* frame; AVPacket* pkt; uint8_t endcode[] = { 0, 0, 1, 0xb7 }; int len = 1920 * 1080 * 3 / 2; uint8_t* buffer = new uint8_t[len]; filename = "D:/Emscripten/cmaketest/20230801230523.264";//编码输出的264，文件没有会自动创建 filename_in = "D:/Emscripten/cmaketest/20230.yuv";//待编码的YUV，YV12；需要有 codec_name = "libx264";//可以自己指定其他编码器 FILE* fpin = fopen(filename_in, "rb+"); if (!fpin) { fprintf(stderr, "Codec '%s' not open\n",filename_in); exit(1); } //查找编码器；还可以使用AVcodec_find_encoder(condec_ID) codec = avcodec_find_encoder_by_name(codec_name); 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 = 1920; c->height = 1080; /* frames per second */ c->time_base.num = 1; c->time_base.den = 25;//时间基1/25 c->framerate.num = 25; //fps=25 c->framerate.den = 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;//YV 12 格式 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, 0); if (ret < 0) { fprintf(stderr, "Could not allocate the video frame data\n"); exit(1); } /* encode 1 second of video */ while (!feof(fpin)) { fflush(stdout); /* Make sure the frame data is writable. On the first round, the frame is fresh from av_frame_get_buffer() and therefore we know it is writable. But on the next rounds, encode() will have called avcodec_send_frame(), and the codec may have kept a reference to the frame in its internal structures, that makes the frame unwritable. av_frame_make_writable() checks that and allocates a new buffer for the frame only if necessary. */ ret = av_frame_make_writable(frame); if (ret < 0) exit(1); /* Prepare a dummy image. In real code, this is where you would have your own logic for filling the frame. FFmpeg does not care what you put in the frame. */ /* Y V,U*/ int res_len = fread(buffer,len ,1,fpin); if (res_len > 0) {//这里可以直接读文件，我是用buffer从中间倒了一手，只要数据对得上，没必要借助中间buffer读数据 frame->data[0] = buffer; frame->data[2] =buffer + frame->width * frame->height; frame->data[1] = buffer + frame->width * frame->height * 5 / 4; frame->pts += 1;//时间基 1/25 /* encode the image */ encode(c, frame, pkt, f); } } /* flush the encoder */ encode(c, NULL, pkt, f); if (codec->id == AV_CODEC_ID_MPEG1VIDEO || codec->id == AV_CODEC_ID_MPEG2VIDEO) fwrite(endcode, 1, sizeof(endcode), f); fclose(f); avcodec_free_context(&c); av_frame_free(&frame); av_packet_free(&pkt); delete[] buffer; fclose(fpin); return 0; } }
效果：
264数据用elecard打开：
这个是我修改 gop =25;无B帧的情况，编码后的数据
