视频编码
cpp
#include <libavutil/log.h>
#include <libavutil/opt.h>
#include <libavcodec/avcodec.h>
static int encode(AVCodecContext *ctx, AVFrame *frame, AVPacket *pkt, FILE *out) {
int ret = -1;
ret = avcodec_send_frame(ctx, frame);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Failed to send frame to encoder\n");
goto _END;
}
while (ret >= 0) {
ret = avcodec_receive_packet(ctx, pkt);
// AVERROR(EAGAIN)表示出错了
if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
return 0;
} else if(ret < 0) {
return -1;
}
fwrite(pkt->data, 1, pkt->size, out);
av_packet_unref(pkt);
}
_END:
return 0;
}
int main(int argc, char *argv[]) {
char *dst = NULL;
char *codecName = NULL;
const AVCodec *codec = NULL;
AVCodecContext *ctx = NULL;
int ret = -1;
FILE *f = NULL;
AVFrame *frame = NULL;
AVPacket *pkt = NULL;
av_log_set_level(AV_LOG_DEBUG);
// 1. 输入参数
if (argc < 3) {
av_log(NULL, AV_LOG_ERROR, "arguments must more than 3\n");
goto _ERROR;
}
dst = argv[1];
codecName = argv[2];
// 2. 查找编码器
codec = avcodec_find_encoder_by_name(codecName);
if (!codec) {
av_log(NULL, AV_LOG_ERROR, "don't find codec name %s\n", codecName);
goto _ERROR;
}
// 3. 创建编码器上下文
ctx = avcodec_alloc_context3(codec);
if (!ctx) {
av_log(NULL, AV_LOG_ERROR, "No memory\n");
goto _ERROR;
}
// 4. 设置编码器参数
ctx->width = 640;
ctx->height = 480;
ctx->bit_rate = 500000;
// 时间基和帧率
ctx->time_base = (AVRational){1, 25};
ctx->framerate = (AVRational){25, 1};
// 设置每10帧一个gop
ctx->gop_size = 10;
// 设置一个gop中最多有一个b帧
ctx->max_b_frames = 1;
// 设置yuv格式
ctx->pix_fmt = AV_PIX_FMT_YUV422P;
if (codec->id == AV_CODEC_ID_H264) {
av_opt_set(ctx->priv_data, "preset", "slow", 0);
}
// 5. 编码器与编码器上下文绑定
ret = avcodec_open2(ctx, codec, NULL);
if (ret < 0) {
av_log(ctx, AV_LOG_ERROR, "Don't open codec: %s", av_err2str(ret));
goto _ERROR;
}
// 6. 创建输出文件
f = fopen(dst, "wb");
if (!f) {
av_log(NULL, AV_LOG_ERROR, "Don't open file %s\n", dst);
goto _ERROR;
}
// 7. 创建AVFrame
frame = av_frame_alloc();
if (!frame) {
av_log(NULL, AV_LOG_ERROR, "No memory\n");
goto _ERROR;
}
// 必须赋值才能获取到buffer
frame->width = ctx->width;
frame->height = ctx->height;
frame->format = ctx->pix_fmt;
// frame中真正存储数据的位置不会被av_frame_alloc生成,还需要调用av_frame_get_buffer获取
ret = av_frame_get_buffer(frame, 0);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Could't not allocate the video frame\n");
goto _ERROR;
}
// 8. 创建AVPacket
pkt = av_packet_alloc();
if (!pkt) {
av_log(NULL, AV_LOG_ERROR, "No memory\n");
goto _ERROR;
}
// 9. 生成视频内容
// 这里是虚拟生成25帧,即一秒钟的数据
for (int i = 0; i < 25; ++i) {
// 确保av_frame中的空间data可用,如果当前data域被锁定了,就会自动指定一个新的data
ret = av_frame_make_writable(frame);
if (ret < 0) {
break;
}
// Y分量
for (int y = 0; y < ctx->height; y++) {
for (int x = 0; x < ctx->width; x++) {
// data[0] 指的是yuv中的y,[frame->linesize[0] 指的是行的大小, x表示横轴位移]
// x + y + i * 3表示Y分量随着x和y变化而渐变
frame->data[0][y * frame->linesize[0] + x] = x + y + i * 3;
}
}
// UV分量
for (int y = 0; y < ctx->height; y++) {
// 对应uv分量 422中都是y分量的一半,所以除以2
for (int x = 0; x < ctx->width / 2; x++) {
// U分量 128在U分量代表黑色, 后面的2是任意的
frame->data[1][y * frame->linesize[1] + x] = 128 + y + i * 2;
// V分量 64在V分量中代表黑色, 后面的5是任意的
frame->data[2][y * frame->linesize[2] + x] = 64 + x + i * 5;
}
}
frame->pts = i;
// 10. 编码
ret = encode(ctx, frame, pkt, f);
if (ret == -1) {
goto _ERROR;
}
}
// 输出一个空包,用于刷新剩余数据
encode(ctx, NULL, pkt, f);
_ERROR:
if (ctx) {
avcodec_free_context(&ctx);
}
if (frame) {
av_frame_free(&frame);
}
if (pkt) {
av_packet_free(&pkt);
}
if (f) {
fclose(f);
}
return 0;
}
shell
gcc -g -o encode_video encode_video.c `pkg-config --libs libavutil libavformat`
./encode_video 1.h264 libx264
音频编码
cpp
#include <libavutil/log.h>
#include <libavutil/opt.h>
#include <libavcodec/avcodec.h>
#include <libavutil/samplefmt.h>
static int select_best_sample_rate(const AVCodec *codec) {
const int *p;
int best_sample_rate = 0;
if (!codec->supported_samplerates) {
return 44100;
}
p = codec->supported_samplerates;
// 找到一个离44100最近的采样率
while (*p) {
if (!best_sample_rate || abs(44100 - *p) < abs(44100 - best_sample_rate)) {
best_sample_rate = *p;
}
p++;
}
return best_sample_rate;
}
// ffmpeg源码自带
static int check_sample_fmt(const AVCodec *codec, enum AVSampleFormat sample_fmt)
{
const enum AVSampleFormat *p = codec->sample_fmts;
while (*p != AV_SAMPLE_FMT_NONE) {
if (*p == sample_fmt)
return 1;
p++;
}
return 0;
}
static int encode(AVCodecContext *ctx, AVFrame *frame, AVPacket *pkt, FILE *out) {
int ret = -1;
ret = avcodec_send_frame(ctx, frame);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Failed to send frame to encoder\n");
goto _END;
}
while (ret >= 0) {
ret = avcodec_receive_packet(ctx, pkt);
// AVERROR(EAGAIN)表示出错了
if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
return 0;
} else if(ret < 0) {
return -1;
}
fwrite(pkt->data, 1, pkt->size, out);
av_packet_unref(pkt);
}
_END:
return 0;
}
int main(int argc, char *argv[]) {
char *dst = NULL;
char *codecName = NULL;
const AVCodec *codec = NULL;
AVCodecContext *ctx = NULL;
int ret = -1;
FILE *f = NULL;
AVFrame *frame = NULL;
AVPacket *pkt = NULL;
uint16_t *samples = NULL;
av_log_set_level(AV_LOG_DEBUG);
// 1. 输入参数
if (argc < 2) {
av_log(NULL, AV_LOG_ERROR, "arguments must more than 2\n");
goto _ERROR;
}
dst = argv[1];
// codecName = argv[2];
// 2. 查找编码器:两种方式,by_name可以使用外部的库,通过CODEC_ID的则使用FFMpeg自带的库
// codec = avcodec_find_encoder_by_name("libx264");
codec = avcodec_find_encoder_by_name("libfdk_aac");
// codec = avcodec_find_encoder(AV_CODEC_ID_AAC); // 用这个会涉及下面注释的一系列修改
if (!codec) {
av_log(NULL, AV_LOG_ERROR, "don't find codec name %s\n", codecName);
goto _ERROR;
}
// 3. 创建编码器上下文
ctx = avcodec_alloc_context3(codec);
if (!ctx) {
av_log(NULL, AV_LOG_ERROR, "No memory\n");
goto _ERROR;
}
// 4. 设置编码器参数
ctx->bit_rate = 64000;
ctx->sample_fmt = AV_SAMPLE_FMT_S16;// AV_SAMPLE_FMT_FLTP,对于ffmpeg内部的编码器 用这个格式
ret = check_sample_fmt(codec, AV_SAMPLE_FMT_S16);
if (ret == 0) {
av_log(NULL, AV_LOG_ERROR, "encoder do not support sample format\n");
goto _ERROR;
}
// 自定义函数找到最接近44100的采样率
ctx->sample_rate = select_best_sample_rate(codec);
// 设置声道布局为立体声stereo
av_channel_layout_copy(&ctx->ch_layout, &(AVChannelLayout)AV_CHANNEL_LAYOUT_STEREO); // AV_CHANNEL_LAYOUT_MONO ffmpeg内部编码器修改成这个
// 5. 编码器与编码器上下文绑定
ret = avcodec_open2(ctx, codec, NULL);
if (ret < 0) {
av_log(ctx, AV_LOG_ERROR, "Don't open codec: %s", av_err2str(ret));
goto _ERROR;
}
// 6. 创建输出文件
f = fopen(dst, "wb");
if (!f) {
av_log(NULL, AV_LOG_ERROR, "Don't open file %s\n", dst);
goto _ERROR;
}
// 7. 创建AVFrame
frame = av_frame_alloc();
if (!frame) {
av_log(NULL, AV_LOG_ERROR, "No memory\n");
goto _ERROR;
}
// 必须赋值才能获取到buffer
frame->nb_samples = ctx->frame_size;
frame->format = ctx->sample_fmt;
av_channel_layout_copy(&frame->ch_layout, &ctx->ch_layout);
// frame中真正存储数据的位置不会被av_frame_alloc生成,还需要调用av_frame_get_buffer获取
ret = av_frame_get_buffer(frame, 0);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Could't not allocate the video frame\n");
goto _ERROR;
}
// 8. 创建AVPacket
pkt = av_packet_alloc();
if (!pkt) {
av_log(NULL, AV_LOG_ERROR, "No memory\n");
goto _ERROR;
}
// 9. 生成音频内容
float t = 0.0;
// 有空了解一下这个值
float tincr = 2 * M_PI * 440 / ctx->sample_rate;
for (int i = 0; i < 200; ++i) {
ret = av_frame_make_writable(frame);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "do not allocate space\n");
goto _ERROR;
}
samples = (uint16_t*)frame->data[0]; // FLTP是32位的 所以改成uint32, 下面所有2都得改成4
// 2字节一个数据
for (int j = 0; j < ctx->frame_size; ++j) {
samples[2 * j] = (sin(t) * 10000);
// 多声道的处理
for (int k = 1; k < ctx->ch_layout.nb_channels; ++k) {
samples[2 * j + k] = samples[2 * j];
}
t += tincr;
}
encode(ctx, frame, pkt, f);
}
// 输出一个空包,用于刷新剩余数据
encode(ctx, NULL, pkt, f);
_ERROR:
if (ctx) {
avcodec_free_context(&ctx);
}
if (frame) {
av_frame_free(&frame);
}
if (pkt) {
av_packet_free(&pkt);
}
if (f) {
fclose(f);
}
return 0;
}
shell
gcc -g -o encode_audio encode_audio.c `pkg-config --libs libavutil libavformat`
./encode_audio 1.aac
由于ffmpeg自带的aac格式是32位的AV_SAMPLE_FMT_FLTP,如果由libfdk_aac转成ffmpeg自带的aac,需要进行重采样成FLTP才能继续其他操作
生成图片
生成黑白色图片
先把视频解码成帧序列,然后将帧保存为图片
cpp
#include <libavformat/avformat.h>
#include <libavutil/log.h>
#include <libavutil/avutil.h>
#include <libavcodec/avcodec.h>
static void savePic(unsigned char *buf, int lineSize, int width, int height, char *name) {
FILE *f;
f = fopen(name, "wb");
// 写入头信息
fprintf(f, "P5\n%d %d\n%d\n", width, height, 255);
for (int i = 0; i < height; ++i) {
fwrite(buf + i *lineSize, 1, width, f);
}
fclose(f);
}
static int decode(AVCodecContext *ctx, AVFrame *frame, AVPacket *pkt, const char *fileName) {
int ret = -1;
char buf[1024];
ret = avcodec_send_packet(ctx, pkt);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Failed to send frame to encoder\n");
goto _END;
}
while (ret >= 0) {
ret = avcodec_receive_frame(ctx, frame);
// AVERROR(EAGAIN)表示出错了
if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
return 0;
} else if(ret < 0) {
return -1;
}
snprintf(buf, sizeof(buf), "%s-%d", fileName, ctx->frame_num);
savePic(frame->data[0], frame->linesize[0], frame->width, frame->height, buf);
if (pkt) {
av_packet_unref(pkt);
}
}
_END:
return 0;
}
int main (int argc, char *argv[]) {
// 1. 处理参数
char *src;
char *dst;
int ret;
int idx = -1;
AVFormatContext *pFmtCtx = NULL;
AVPacket *pkt = NULL;
const AVCodec *codec = NULL;
AVCodecContext *ctx = NULL;
AVFrame *frame = NULL;
AVStream *inStream = NULL;
av_log_set_level(AV_LOG_DEBUG);
if (argc < 3) {
av_log(NULL, AV_LOG_ERROR, "argument must be more than 3\n");
exit(-1);
}
src = argv[1];
dst = argv[2];
// 2. 打开多媒体文件
ret = avformat_open_input(&pFmtCtx, src, NULL, NULL);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "%s\n", av_err2str(ret));
exit(-1);
}
// 3. 从多媒体文件中找到音频流
idx = av_find_best_stream(pFmtCtx, AVMEDIA_TYPE_VIDEO, -1, -1, NULL, 0);
if (idx < 0) {
av_log(pFmtCtx, AV_LOG_ERROR, "Does not include audio stream\n");
goto _ERROR;
}
inStream = pFmtCtx->streams[idx];
// 4. 查找解码器
codec = avcodec_find_decoder(inStream->codecpar->codec_id);
if (!codec) {
av_log(NULL, AV_LOG_ERROR, "don't find codec\n");
goto _ERROR;
}
// 5. 创建解码器上下文
ctx = avcodec_alloc_context3(codec);
if (!ctx) {
av_log(NULL, AV_LOG_ERROR, "No memory\n");
goto _ERROR;
}
// 拷贝编码参数到上下文对象
avcodec_parameters_to_context(ctx, inStream->codecpar);
// 5. 解码器与解码器上下文绑定
ret = avcodec_open2(ctx, codec, NULL);
if (ret < 0) {
av_log(ctx, AV_LOG_ERROR, "Don't open codec: %s", av_err2str(ret));
goto _ERROR;
}
// 6. 创建AVFrame
frame = av_frame_alloc();
if (!frame) {
av_log(NULL, AV_LOG_ERROR, "No memory\n");
goto _ERROR;
}
// 7. 创建AVPacket
pkt = av_packet_alloc();
if (!pkt) {
av_log(NULL, AV_LOG_ERROR, "No memory\n");
goto _ERROR;
}
// 8. 从源多媒体文件中读数据到目的文件中
while (av_read_frame(pFmtCtx, pkt) >= 0) {
if (pkt->stream_index == idx) {
decode(ctx, frame, pkt, dst);
}
}
decode(ctx, frame, NULL, dst);
// 9. 将申请的资源释放掉
_ERROR:
if (pFmtCtx) {
avformat_close_input(&pFmtCtx);
pFmtCtx = NULL;
}
if (ctx) {
avcodec_free_context(&ctx);
ctx = NULL;
}
if (frame) {
av_frame_free(&frame);
frame = NULL;
}
if (pkt) {
av_packet_free(&pkt);
pkt = NULL;
}
return 0;
}
shell
gcc -g -o gen_pic gen_pic.c `pkg-config --libs libavutil libavformat`
./gen_pic ~/resource/1.mp4 out/out
生成彩色图片BMP
这个代码有太多写死的内容了
cpp
#include <libavformat/avformat.h>
#include <libavutil/log.h>
#include <libavutil/avutil.h>
#include <libavcodec/avcodec.h>
#include <libswscale/swscale.h>
#define WORD uint16_t
#define DWORD uint32_t
#define LONG int32_t
// 去网站上拷贝对应定义:https://learn.microsoft.com/zh-cn/windows/win32/api/wingdi/ns-wingdi-bitmapinfoheader
typedef struct tagBITMAPINFOHEADER {
DWORD biSize;
LONG biWidth;
LONG biHeight;
WORD biPlanes;
WORD biBitCount;
DWORD biCompression;
DWORD biSizeImage;
LONG biXPelsPerMeter;
LONG biYPelsPerMeter;
DWORD biClrUsed;
DWORD biClrImportant;
} BITMAPINFOHEADER, *LPBITMAPINFOHEADER, *PBITMAPINFOHEADER;
#pragma pack(2)
typedef struct tagBITMAPFILEHEADER {
WORD bfType;
DWORD bfSize;
WORD bfReserved1;
WORD bfReserved2;
DWORD bfOffBits;
} BITMAPFILEHEADER, *LPBITMAPFILEHEADER, *PBITMAPFILEHEADER;
static void saveBMP(struct SwsContext *swsCtx,
AVFrame *frame, int w, int h, char *name) {
FILE *f = NULL;
// 3是因为转换成24位的帧,刚好3个字节
int dataSize = w * h * 3;
// 1. 进行转换,将yuv frame 转成 BRG24 Frame
AVFrame *frameBGR = av_frame_alloc();
frameBGR->width = w;
frameBGR->height = h;
frameBGR->format = AV_PIX_FMT_BGR24;
av_frame_get_buffer(frameBGR, 0);
sws_scale(swsCtx,
(const uint8_t *const *)frame->data,
frame->linesize,
0,
frame->height,
frameBGR->data,
frameBGR->linesize);
// 2. 构造 BITMAP INFO HEADER
BITMAPINFOHEADER infoHeader;
infoHeader.biSize = sizeof(BITMAPINFOHEADER);
infoHeader.biWidth = w;
infoHeader.biHeight = h * (-1); // 坐标与正常坐标相反
infoHeader.biBitCount = 24;
infoHeader.biCompression = 0;
infoHeader.biSizeImage = 0;
infoHeader.biClrImportant = 0;
infoHeader.biClrUsed = 0;
infoHeader.biXPelsPerMeter = 0;
infoHeader.biYPelsPerMeter = 0;
infoHeader.biPlanes = 1;
// 3. 构造 BITMAP FILE HEADER
BITMAPFILEHEADER fileHeader = {0, };
fileHeader.bfType = 0x4d42; // 表示两个字符'BM'
fileHeader.bfSize = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER) + dataSize;
fileHeader.bfOffBits = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
// 4. 将数据写到文件
f = fopen(name, "wb");
fwrite(&fileHeader, sizeof(BITMAPFILEHEADER), 1, f);
fwrite(&infoHeader, sizeof(BITMAPINFOHEADER), 1, f);
fwrite(frameBGR->data[0], 1, dataSize, f);
// 5. 释放资源
fclose(f);
av_freep(&frameBGR->data[0]);
av_free(frameBGR);
}
static void savePic(unsigned char *buf, int lineSize, int width, int height, char *name) {
FILE *f;
f = fopen(name, "wb");
// 写入头信息
fprintf(f, "P5\n%d %d\n%d\n", width, height, 255);
for (int i = 0; i < height; ++i) {
fwrite(buf + i * lineSize, 1, width, f);
}
fclose(f);
}
static int decode(AVCodecContext *ctx, struct SwsContext *swsCtx,
AVFrame *frame, AVPacket *pkt, const char *fileName) {
int ret = -1;
char buf[1024];
ret = avcodec_send_packet(ctx, pkt);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Failed to send frame to encoder\n");
goto _END;
}
while (ret >= 0) {
ret = avcodec_receive_frame(ctx, frame);
// AVERROR(EAGAIN)表示出错了
if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
return 0;
} else if(ret < 0) {
return -1;
}
snprintf(buf, sizeof(buf), "%s-%d.bmp", fileName, ctx->frame_num);
// savePic(frame->data[0], frame->linesize[0], frame->width, frame->height, buf);
saveBMP(swsCtx, frame, 640, 360, buf);
// 释放前需要判空
if (pkt) {
av_packet_unref(pkt);
}
}
_END:
return 0;
}
int main (int argc, char *argv[]) {
// 1. 处理参数
char *src;
char *dst;
int ret = -1;
int idx = -1;
AVFormatContext *pFmtCtx = NULL;
AVPacket *pkt = NULL;
const AVCodec *codec = NULL;
AVCodecContext *ctx = NULL;
AVFrame *frame = NULL;
AVStream *inStream = NULL;
struct SwsContext *swsCtx = NULL;
av_log_set_level(AV_LOG_DEBUG);
if (argc < 3) {
av_log(NULL, AV_LOG_ERROR, "argument must be more than 3\n");
exit(-1);
}
src = argv[1];
dst = argv[2];
// 2. 打开多媒体文件
ret = avformat_open_input(&pFmtCtx, src, NULL, NULL);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "%s\n", av_err2str(ret));
exit(-1);
}
// 3. 从多媒体文件中找到音频流
idx = av_find_best_stream(pFmtCtx, AVMEDIA_TYPE_VIDEO, -1, -1, NULL, 0);
if (idx < 0) {
av_log(pFmtCtx, AV_LOG_ERROR, "Does not include audio stream\n");
goto _ERROR;
}
inStream = pFmtCtx->streams[idx];
// 4. 查找解码器
codec = avcodec_find_decoder(inStream->codecpar->codec_id);
if (!codec) {
av_log(NULL, AV_LOG_ERROR, "don't find codec\n");
goto _ERROR;
}
// 5. 创建解码器上下文
ctx = avcodec_alloc_context3(NULL);
if (!ctx) {
av_log(NULL, AV_LOG_ERROR, "No memory\n");
goto _ERROR;
}
// 拷贝编码参数到上下文对象
avcodec_parameters_to_context(ctx, inStream->codecpar);
// 5. 解码器与解码器上下文绑定
ret = avcodec_open2(ctx, codec, NULL);
if (ret < 0) {
av_log(ctx, AV_LOG_ERROR, "Don't open codec: %s", av_err2str(ret));
goto _ERROR;
}
av_log(NULL, AV_LOG_INFO, "scale: %d, %d\n", ctx->width, ctx->height);
// 5.1 获得SWS上下文
swsCtx = sws_getContext(ctx->width, // src width
ctx->height, // src height
AV_PIX_FMT_YUV420P, // src pix fmt 有时候ctx->pix_fmt的格式是不对的
640, // dst width 这里的640 x 360 是因为需要按比例
360, // dst height
AV_PIX_FMT_BGR24, // dst pix fmt
SWS_BICUBIC, // 后面研究
NULL, NULL, NULL);
if (!swsCtx) {
av_log(NULL, AV_LOG_ERROR, "Could not get swscale Context\n");
goto _ERROR;
}
// 6. 创建AVFrame
frame = av_frame_alloc();
if (!frame) {
av_log(NULL, AV_LOG_ERROR, "No memory\n");
goto _ERROR;
}
// 7. 创建AVPacket
pkt = av_packet_alloc();
if (!pkt) {
av_log(NULL, AV_LOG_ERROR, "No memory\n");
goto _ERROR;
}
// 8. 从源多媒体文件中读数据到目的文件中
while (av_read_frame(pFmtCtx, pkt) >= 0) {
if (pkt->stream_index == idx) {
decode(ctx, swsCtx, frame, pkt, dst);
}
}
decode(ctx, swsCtx, frame, NULL, dst);
// 9. 将申请的资源释放掉
_ERROR:
if (pFmtCtx) {
avformat_close_input(&pFmtCtx);
pFmtCtx = NULL;
}
if (ctx) {
avcodec_free_context(&ctx);
ctx = NULL;
}
if (frame) {
av_frame_free(&frame);
frame = NULL;
}
if (pkt) {
av_packet_free(&pkt);
pkt = NULL;
}
if (swsCtx) {
sws_freeContext(swsCtx);
swsCtx = NULL;
}
return 0;
}
shell
gcc -g -o gen_pic gen_pic.c `pkg-config --libs libavutil libavformat libswscale`
./gen_pic ~/resource/1.mp4 out/out