利用qt和ffmpeg軟體來製作視頻裁剪工具

0 什麼是ffmpeg?

Libav（舊稱：FFmpeg）是一個自由軟體，可以運行音頻和視頻多種格式的錄影、轉檔、流功能^{[1]，包含了libavcodec
─這是一個用於多個專案中音頻和視頻的解碼器庫，以及 libavformat ——一個音頻與視頻格式轉換庫。}

libav的舊稱"FFmpeg"這個單詞中的 "FF" 指的是 "Fast Forward"^{[2]。有些新手寫信給"FFmpeg"的項目負責人，詢問FF是不是代表“Fast
Free”或者“Fast Fourier”等意思，"FFmpeg"的項目負責人回信說“Just for the record, the original meaning of "FF" in FFmpeg is "Fast Forward"...”}

http://zh.wikipedia.org/wiki/Libav

 

 一 下載ffmpeg

官方網站：     http://ffmpeg.zeranoe.com/

訪問               http://ffmpeg.zeranoe.com/builds/

下載ffmpeg windows下發布版

FFmpeg
git-f514695 32-bit Shared (Latest) 

 

二 在命令列下學會ffmpeg使用

cd 進入ffmpeg解壓縮目錄下的bin目錄

ffmpeg.exe -i D:/source.avi -vcodec copy -y -r 25 -ss 8 -t 971 D:/demo.mp4  >> D:\clip_info.txt 2>&1

 

這裡-vcodec copy參數一定要加，這樣裁剪的時候不會改變視頻的編碼方式，裁剪非常快。

 

ffmpeg主要參數一覽

Hyper fast Audio and Video encoder

usage: ffmpeg [options] [[infile options] -i infile]... {[outfile options] outfile}...

Main options:
-L                  show license
-h                  show help
-?                  show help
-help               show help
--help              show help
-version            show version
-formats            show available formats
-codecs             show available codecs
-bsfs               show available bit stream filters
-protocols          show available protocols
-filters            show available filters
-pix_fmts           show available pixel formats
-sample_fmts        show available audio sample formats
-loglevel loglevel  set libav* logging level
-v loglevel         set libav* logging level
-debug flags        set debug flags
-report             generate a report
-max_alloc bytes    set maximum size of a single allocated block
-f fmt              force format
-i filename         input file name
-y                  overwrite output files
-n                  do not overwrite output files
-c codec            codec name
-codec codec        codec name
-pre preset         preset name
-map_metadata outfile[,metadata]:infile[,metadata]  set metadata information of outfile from infile
-t duration         record or transcode "duration" seconds of audio/video
-fs limit_size      set the limit file size in bytes
-ss time_off        set the start time offset
-itsoffset time_off  set the input ts offset
-itsscale scale     set the input ts scale
-timestamp time     set the recording timestamp ('now' to set the current time)
-metadata string=string  add metadata
-dframes number     set the number of data frames to record
-timelimit limit    set max runtime in seconds
-target type        specify target file type ("vcd", "svcd", "dvd", "dv", "dv50", "pal-vcd", "ntsc-svcd", ...)
-xerror             exit on error
-frames number      set the number of frames to record
-tag fourcc/tag     force codec tag/fourcc
-filter filter_list  set stream filterchain
-stats              print progress report during encoding
-attach filename    add an attachment to the output file
-dump_attachment filename  extract an attachment into a file
-bsf bitstream_filters  A comma-separated list of bitstream filters
-dcodec codec       force data codec ('copy' to copy stream)

Advanced options:
-map [-]input_file_id[:stream_specifier][,sync_file_id[:stream_s  set input stream mapping
-map_channel file.stream.channel[:syncfile.syncstream]  map an audio channel from one stream to another
-map_chapters input_file_index  set chapters mapping
-benchmark          add timings for benchmarking
-dump               dump each input packet
-hex                when dumping packets, also dump the payload
-re                 read input at native frame rate
-loop_input         deprecated, use -loop
-loop_output        deprecated, use -loop
-vsync              video sync method
-async              audio sync method
-adrift_threshold threshold  audio drift threshold
-copyts             copy timestamps
-copytb source      copy input stream time base when stream copying
-shortest           finish encoding within shortest input
-dts_delta_threshold threshold  timestamp discontinuity delta threshold
-copyinkf           copy initial non-keyframes
-q q                use fixed quality scale (VBR)
-qscale q           use fixed quality scale (VBR)
-streamid streamIndex:value  set the value of an outfile streamid
-muxdelay seconds   set the maximum demux-decode delay
-muxpreload seconds  set the initial demux-decode delay
-fpre filename      set options from indicated preset file

Video options:
-vframes number     set the number of video frames to record
-r rate             set frame rate (Hz value, fraction or abbreviation)
-s size             set frame size (WxH or abbreviation)
-aspect aspect      set aspect ratio (4:3, 16:9 or 1.3333, 1.7777)
-bits_per_raw_sample number  set the number of bits per raw sample
-croptop size       Removed, use the crop filter instead
-cropbottom size    Removed, use the crop filter instead
-cropleft size      Removed, use the crop filter instead
-cropright size     Removed, use the crop filter instead
-padtop size        Removed, use the pad filter instead
-padbottom size     Removed, use the pad filter instead
-padleft size       Removed, use the pad filter instead
-padright size      Removed, use the pad filter instead
-padcolor color     Removed, use the pad filter instead
-vn                 disable video
-vcodec codec       force video codec ('copy' to copy stream)
-sameq              use same quantizer as source (implies VBR)
-same_quant         use same quantizer as source (implies VBR)
-pass n             select the pass number (1 or 2)
-passlogfile prefix  select two pass log file name prefix
-vf filter list     video filters
-b bitrate          video bitrate (please use -b:v)
-dn                 disable data

 

三 利用QT4做個簡單圖形介面工具

 

 

這裡主要用了QProcess這個類，可以調用外部程式。

關鍵代碼： 

 

    QString program = "D:\\maxview_video_demo\\ffmpeg\\ffmpeg-git-985e768-win64-static\\bin\\ffmpeg.exe";
    QString inputPath = ui->videopathLineEdit->text();
    QFile sourceFile(inputPath);
    if(!sourceFile.exists()){
        QMessageBox::information(this,QString::fromUtf8("提示"),QString::fromUtf8("找不到源檔案"));
        return;
    }

    QString outputPath = QFileInfo(sourceFile).absolutePath() +"/clip.mp4";

    QFile destFile(outputPath);
    if(destFile.exists()){
        destFile.remove();
    }

    QString startTime = ui->videoStartTimeEdit->time().toString("hh:mm:ss");
    QString len= ui->videoLengthTimeEdit->time().toString("hh:mm:ss");
    QStringList arguments;
    arguments << "-i" << inputPath << "-r" << "25"<<"-ss";
    arguments <<startTime<< "-t" << len<< outputPath;

    QProcess *clipProcess = new QProcess(this);
    connect(clipProcess,SIGNAL(finished(int)),this,SLOT(clipVideoFinished(int)));

    clipProcess->start(program, arguments);

 

當視頻截取完成後，進程會發生訊號finished(int)，並被QProcess捕捉到，這樣可以調用

clipVideoFinished函數來通知程式視頻裁剪完成了。