方法1：命令修改分辨率
# 修改分辨率
ffmpeg -i input.mp4 -vf scale=1280:1024 -f rawvideo output.yuv
# 播放
ffplay -s 1280*1024 -pix_fmt yuv420p output.yuv方法2：代码转换
main.c
#include "libavutil/log.h"
#include "libavformat/avformat.h"
#include "libavutil/avutil.h"
#include "libavcodec/avcodec.h"
#include "libavutil/parseutils.h"
#include "libswscale/swscale.h"
#include "libavutil/imgutils.h"
int decodeVideo(AVCodecContext *codecCtx, AVPacket *packet,struct SwsContext *c,int dstWeight,int dstHeight,AVFrame *dstFrame,FILE *dst) {
int ret = avcodec_send_packet(codecCtx, packet);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "avcodec_send_packet failed: %s\n", av_err2str(ret));
av_packet_unref(packet);
return ret;
}
AVFrame *frame = av_frame_alloc();
while ((ret = avcodec_receive_frame(codecCtx, frame)) == 0) {
sws_scale(c, (const uint8_t *const *) frame->data, frame->linesize, 0, codecCtx->height, dstFrame->data, dstFrame->linesize);
fwrite(dstFrame->data[0], 1, dstWeight * dstHeight, dst); // Y data
fwrite(dstFrame->data[1], 1, dstWeight * dstHeight / 4, dst); // U data
fwrite(dstFrame->data[2], 1, dstWeight * dstHeight / 4, dst); // V data
}
if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
av_frame_free(&frame);
return 0;
} else if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "avcodec_receive_frame failed: %s\n", av_err2str(ret));
av_frame_free(&frame);
return ret;
}
av_frame_free(&frame);
return 0;
}
int main(int argc, char **argv) {
av_log_set_level(AV_LOG_DEBUG);
if (argc < 4) {
av_log(NULL, AV_LOG_ERROR, "Usage: %s inputFile outputFile\n", argv[0]);
return -1;
}
const char *inputFile = argv[1];
const char *outputFile = argv[2];
const char *dstVideoSizeString = argv[3];
int ret;
int dstHeight = 0;
int dstWeight = 0;
ret = av_parse_video_size(&dstWeight, &dstHeight, dstVideoSizeString);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "av_parse_video_size failed: %s\n", inputFile, av_err2str(ret));
return -1;
}
AVFormatContext *fCtx = NULL;
if ((ret = avformat_open_input(&fCtx, inputFile, NULL, NULL)) < 0) {
av_log(NULL, AV_LOG_ERROR, "Open input file %s failed: %s\n", inputFile, av_err2str(ret));
return -1;
}
if ((ret = avformat_find_stream_info(fCtx, NULL)) < 0) {
av_log(NULL, AV_LOG_ERROR, "Find input file stream info failed: %s\n", av_err2str(ret));
avformat_close_input(&fCtx);
return -1;
}
ret = av_find_best_stream(fCtx, AVMEDIA_TYPE_VIDEO, -1, -1, NULL, 0);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "av_find_best_stream failed: %s\n", av_err2str(ret));
avformat_close_input(&fCtx);
return -1;
}
int videoIndex = ret;
AVCodecContext *codecCtx = avcodec_alloc_context3(NULL);
if (codecCtx == NULL) {
av_log(NULL, AV_LOG_ERROR, "avcodec_alloc_context3 failed\n");
avformat_close_input(&fCtx);
return -1;
}
if ((ret = avcodec_parameters_to_context(codecCtx, fCtx->streams[videoIndex]->codecpar)) < 0) {
av_log(NULL, AV_LOG_ERROR, "avcodec_parameters_to_context failed: %s\n", av_err2str(ret));
avformat_close_input(&fCtx);
avcodec_free_context(&codecCtx);
return -1;
}
AVCodec *decoder = avcodec_find_decoder(codecCtx->codec_id);
if (decoder == NULL) {
av_log(NULL, AV_LOG_ERROR, "avcodec_find_decoder failed\n");
avformat_close_input(&fCtx);
avcodec_free_context(&codecCtx);
return -1;
}
if ((ret = avcodec_open2(codecCtx, decoder, NULL)) < 0) {
av_log(NULL, AV_LOG_ERROR, "avcodec_open2 failed: %s\n", av_err2str(ret));
avformat_close_input(&fCtx);
avcodec_free_context(&codecCtx);
return -1;
}
enum AVPixelFormat dstFormat = codecCtx->pix_fmt;
struct SwsContext *swsCtx = sws_getContext(codecCtx->width, codecCtx->height, codecCtx->pix_fmt,
dstWeight, dstHeight, dstFormat,
SWS_FAST_BILINEAR, NULL, NULL, NULL);
if (swsCtx==NULL){
av_log(NULL, AV_LOG_ERROR, "sws_getContext failed\n");
avformat_close_input(&fCtx);
avcodec_free_context(&codecCtx);
return -1;
}
AVFrame *dstFrame = av_frame_alloc();
ret = av_image_get_buffer_size(dstFormat,dstWeight,dstHeight,1);
if (ret<0){
av_log(NULL, AV_LOG_ERROR, "av_image_get_buffer_size failed:%s\n", av_err2str(ret));
avformat_close_input(&fCtx);
avcodec_free_context(&codecCtx);
return -1;
}
uint8_t *outBuffer = av_malloc(ret);
av_image_fill_arrays(dstFrame->data,dstFrame->linesize,outBuffer,dstFormat,dstWeight,dstHeight,1);
FILE *dst = fopen(outputFile, "wb");
if (dst == NULL) {
av_log(NULL, AV_LOG_ERROR, "open outputFile failed\n");
avformat_close_input(&fCtx);
avcodec_free_context(&codecCtx);
return -1;
}
AVPacket *packet = av_packet_alloc();
if (!packet) {
av_log(NULL, AV_LOG_ERROR, "Could not allocate AVPacket\n");
avformat_close_input(&fCtx);
avcodec_free_context(&codecCtx);
fclose(dst);
return -1;
}
while (av_read_frame(fCtx, packet) == 0) {
if (packet->stream_index == videoIndex) {
if (decodeVideo(codecCtx, packet, swsCtx,dstWeight,dstHeight,dstFrame,dst) < 0) {
av_packet_unref(packet);
break;
}
}
av_packet_unref(packet);
}
decodeVideo(codecCtx, NULL, swsCtx,dstWeight,dstHeight,dstFrame,dst);
// Cleanup
av_packet_free(&packet);
avformat_close_input(&fCtx);
avcodec_free_context(&codecCtx);
fclose(dst);
av_frame_free(&dstFrame);
return 0;
}Makefile
TARGET=main
SRC=main.c
CC=gcc
CFLAGS=-I /usr/local/ffmpeg/include
LDFLAGS=-L /usr/local/ffmpeg/lib
LDFLAGS+= -lavutil -lavformat -lavcodec -lswscale
all:$(TARGET)
$(TARGET):$(SRC)
$(CC) $(SRC) $(CFLAGS) $(LDFLAGS) -o $(TARGET)
clean:
rm -rf $(TARGET)
