从0到建网站,免费自建网站步骤,深圳微信公众号,麻涌镇网站建设视频慢动作处理是个比较常用的操作#xff0c;可以在播放的时候处理#xff0c;这里我们考虑把视频修改为慢动作#xff0c;使用ffmpeg命令#xff0c;可以这样
ffmpeg -i test.mp4 -vf setpts5*PTS -an test_slow3.mp4
这里把视频放慢了5倍#xff0c;生成…视频慢动作处理是个比较常用的操作可以在播放的时候处理这里我们考虑把视频修改为慢动作使用ffmpeg命令可以这样
ffmpeg -i test.mp4 -vf setpts5*PTS -an test_slow3.mp4
这里把视频放慢了5倍生成的文件大小也变大了几倍。
怎么用程序来实现呢参考一下GPT给出的code
#include iostream
#include string
#include cstdlib
#include cstring
extern C {
#include libavformat/avformat.h
#include libavcodec/avcodec.h
#include libavutil/opt.h
}// 慢速播放的速度因子
const double SLOWDOWN_FACTOR 2.0;int main(int argc, char* argv[]) {if (argc 3) {std::cout Usage: argv[0] input_file output_file std::endl;return 1;}const std::string inputFileName argv[1];const std::string outputFileName argv[2];av_register_all();AVFormatContext* inputFormatContext nullptr;if (avformat_open_input(inputFormatContext, inputFileName.c_str(), nullptr, nullptr) ! 0) {std::cerr Failed to open input file: inputFileName std::endl;return 1;}if (avformat_find_stream_info(inputFormatContext, nullptr) 0) {std::cerr Failed to retrieve input stream information std::endl;avformat_close_input(inputFormatContext);return 1;}AVFormatContext* outputFormatContext nullptr;if (avformat_alloc_output_context2(outputFormatContext, nullptr, nullptr, outputFileName.c_str()) 0) {std::cerr Failed to allocate output format context std::endl;avformat_close_input(inputFormatContext);return 1;}for (unsigned int i 0; i inputFormatContext-nb_streams; i) {AVStream* inputStream inputFormatContext-streams[i];AVStream* outputStream avformat_new_stream(outputFormatContext, nullptr);if (!outputStream) {std::cerr Failed to allocate output stream std::endl;avformat_close_input(inputFormatContext);avformat_free_context(outputFormatContext);return 1;}if (avcodec_parameters_copy(outputStream-codecpar, inputStream-codecpar) 0) {std::cerr Failed to copy codec parameters std::endl;avformat_close_input(inputFormatContext);avformat_free_context(outputFormatContext);return 1;}outputStream-time_base inputStream-time_base;}if (!(outputFormatContext-oformat-flags AVFMT_NOFILE)) {if (avio_open(outputFormatContext-pb, outputFileName.c_str(), AVIO_FLAG_WRITE) 0) {std::cerr Failed to open output file: outputFileName std::endl;avformat_close_input(inputFormatContext);avformat_free_context(outputFormatContext);return 1;}}if (avformat_write_header(outputFormatContext, nullptr) 0) {std::cerr Failed to write output file header std::endl;avformat_close_input(inputFormatContext);avformat_free_context(outputFormatContext);return 1;}AVPacket packet;while (av_read_frame(inputFormatContext, packet) 0) {AVStream* outputStream outputFormatContext-streams[packet.stream_index];// 慢速播放的时间戳调整packet.pts * static_castint64_t(SLOWDOWN_FACTOR);packet.dts * static_castint64_t(SLOWDOWN_FACTOR);packet.duration static_castint(packet.duration * SLOWDOWN_FACTOR);av_interleaved_write_frame(outputFormatContext, packet);av_packet_unref(packet);}av_write_trailer(outputFormatContext);avformat_close_input(inputFormatContext);avformat_free_context(outputFormatContext);return 0;
}
这个代码执行后并没有实现变慢参考一下进行修改后可以实现慢动作处理如下 int slow() {std::string filename test.mp4; // 输入MP4文件名std::string outputFilename test_slow.mp4; // 输出图片文件名AVFormatContext* ofmt_ctx nullptr;avformat_alloc_output_context2(ofmt_ctx, NULL, NULL, outputFilename.c_str());const AVOutputFormat* ofmt ofmt_ctx-oformat;AVFormatContext* formatContext nullptr;if (avformat_open_input(formatContext, filename.c_str(), nullptr, nullptr) ! 0) {std::cerr Error opening input file std::endl;return -1;}if (avformat_find_stream_info(formatContext, nullptr) 0) {std::cerr Error finding stream information std::endl;avformat_close_input(formatContext);return -1;}const AVCodec* codec nullptr;int videoStreamIndex -1;for (unsigned int i 0; i formatContext-nb_streams; i) {if (formatContext-streams[i]-codecpar-codec_type AVMEDIA_TYPE_VIDEO) {videoStreamIndex i;codec avcodec_find_decoder(formatContext-streams[i]-codecpar-codec_id);//AVStream* out_stream avformat_new_stream(ofmt_ctx, NULL);avcodec_parameters_copy(out_stream-codecpar, formatContext-streams[i]-codecpar);out_stream-codecpar-codec_tag 0;break;}}avio_open(ofmt_ctx-pb, outputFilename.c_str(), AVIO_FLAG_WRITE);avformat_write_header(ofmt_ctx, NULL);AVPacket packet;av_init_packet(packet);// 计算目标时间戳int64_t targetTimestamp targetSecond * AV_TIME_BASE;// 查找目标时间戳所对应的帧AVFrame* frame av_frame_alloc();bool foundTargetFrame false;int count 0;while (av_read_frame(formatContext, packet) 0) {if (packet.stream_index videoStreamIndex) {AVStream* inputStream formatContext-streams[packet.stream_index];AVStream* outputStream ofmt_ctx-streams[packet.stream_index];// 计算新的时间戳cout 1, pts packet.pts endl;packet.pts av_rescale_q_rnd(packet.pts, inputStream-time_base, outputStream-time_base, AV_ROUND_NEAR_INF);packet.dts av_rescale_q_rnd(packet.dts, inputStream-time_base, outputStream-time_base, AV_ROUND_NEAR_INF);packet.duration av_rescale_q(packet.duration, inputStream-time_base, outputStream-time_base);packet.pos -1;cout 2, pts packet.pts endl;// 慢速播放的时间戳调整packet.pts * 5;packet.dts * 5;packet.duration * 5;// av_log(NULL, AV_LOG_INFO, ...av_write_frame(ofmt_ctx, packet);\n);int ret av_write_frame(ofmt_ctx, packet);if (ret 0) {std::cerr Error av_write_frame std::endl;}count;}av_packet_unref(packet);}av_write_trailer(ofmt_ctx);return 1;
}通过pts的修改来实现
