嘿 stackoverflow 朋友们，
我需要使用 FFmpeg 将一个视频和几张照片组合起来创建一个视频。 我已经设法在我的系统上编译 FFmpeg 并静态链接它。 现在我正在寻找使用 ffmpeg 来完成任务的包装器/库，适用于 Android。
我尝试过的：
所以问题仍然存在，有哪些适用于 Android 的好的 FFmpeg 包装器？
【问题讨论】：
标签： android video ffmpeg wrapper codec
这是完美运行的 FFMPEG 包装器：您必须按照以下步骤为 android 制作 FFMPEG 包装器。您必须创建几个类，如下所示：
ShellUtils.java
package com.example.processvideo;
public class ShellUtils {
//various console cmds
public final static String SHELL_CMD_CHMOD = "chmod";
public final static String SHELL_CMD_KILL = "kill -9";
public final static String SHELL_CMD_RM = "rm";
public final static String SHELL_CMD_PS = "ps";
public final static String SHELL_CMD_PIDOF = "pidof";
public final static String CHMOD_EXE_VALUE = "700";
public static boolean isRootPossible()
{
StringBuilder log = new StringBuilder();
try {
// Check if Superuser.apk exists
File fileSU = new File("/system/app/Superuser.apk");
if (fileSU.exists())
return true;
fileSU = new File("/system/bin/su");
if (fileSU.exists())
return true;
//Check for 'su' binary
String[] cmd = {"which su"};
int exitCode = ShellUtils.doShellCommand(cmd, new ShellCallback ()
{
@Override
public void shellOut(char[] msg) {
//System.out.print(msg);
}
}, false, true);
if (exitCode == 0) {
logMessage("Can acquire root permissions");
return true;
}
} catch (IOException e) {
//this means that there is no root to be had (normally) so we won't log anything
logException("Error checking for root access",e);
}
catch (Exception e) {
logException("Error checking for root access",e);
//this means that there is no root to be had (normally)
}
logMessage("Could not acquire root permissions");
return false;
}
public static int findProcessId(String command)
{
int procId = -1;
try
{
procId = findProcessIdWithPidOf(command);
if (procId == -1)
procId = findProcessIdWithPS(command);
}
catch (Exception e)
{
try
{
procId = findProcessIdWithPS(command);
}
catch (Exception e2)
{
logException("Unable to get proc id for: " + command,e2);
}
}
return procId;
}
//use 'pidof' command
public static int findProcessIdWithPidOf(String command) throws Exception
{
int procId = -1;
Runtime r = Runtime.getRuntime();
Process procPs = null;
String baseName = new File(command).getName();
//fix contributed my mikos on 2010.12.10
procPs = r.exec(new String[] {SHELL_CMD_PIDOF, baseName});
//procPs = r.exec(SHELL_CMD_PIDOF);
BufferedReader reader = new BufferedReader(new InputStreamReader(procPs.getInputStream()));
String line = null;
while ((line = reader.readLine())!=null)
{
try
{
//this line should just be the process id
procId = Integer.parseInt(line.trim());
break;
}
catch (NumberFormatException e)
{
logException("unable to parse process pid: " + line,e);
}
}
return procId;
}
//use 'ps' command
public static int findProcessIdWithPS(String command) throws Exception
{
int procId = -1;
Runtime r = Runtime.getRuntime();
Process procPs = null;
procPs = r.exec(SHELL_CMD_PS);
BufferedReader reader = new BufferedReader(new InputStreamReader(procPs.getInputStream()));
String line = null;
while ((line = reader.readLine())!=null)
{
if (line.indexOf(' ' + command)!=-1)
{
StringTokenizer st = new StringTokenizer(line," ");
st.nextToken(); //proc owner
procId = Integer.parseInt(st.nextToken().trim());
break;
}
}
return procId;
}
public static int doShellCommand(String[] cmds, ShellCallback sc, boolean runAsRoot, boolean waitFor) throws Exception
{
Process proc = null;
int exitCode = -1;
if (runAsRoot)
proc = Runtime.getRuntime().exec("su");
else
proc = Runtime.getRuntime().exec("sh");
OutputStreamWriter out = new OutputStreamWriter(proc.getOutputStream());
for (int i = 0; i < cmds.length; i++)
{
logMessage("executing shell cmd: " + cmds[i] + "; runAsRoot=" + runAsRoot + ";waitFor=" + waitFor);
out.write(cmds[i]);
out.write("\n");
}
out.flush();
out.write("exit\n");
out.flush();
if (waitFor)
{
final char buf[] = new char[20];
// Consume the "stdout"
InputStreamReader reader = new InputStreamReader(proc.getInputStream());
int read=0;
while ((read=reader.read(buf)) != -1) {
if (sc != null) sc.shellOut(buf);
}
// Consume the "stderr"
reader = new InputStreamReader(proc.getErrorStream());
read=0;
while ((read=reader.read(buf)) != -1) {
if (sc != null) sc.shellOut(buf);
}
exitCode = proc.waitFor();
}
return exitCode;
}
public static void logMessage (String msg)
{
}
public static void logException (String msg, Exception e)
{
}
public interface ShellCallback
{
public void shellOut (char[] msg);
}
}
RegionTrail.java 公共类 RegionTrail {
private HashMap<Integer,ObscureRegion> regionMap = new HashMap<Integer,ObscureRegion>();
private int startTime = 0;
private int endTime = 0;
public static final String OBSCURE_MODE_REDACT = "black";
public static final String OBSCURE_MODE_PIXELATE = "pixel";
private String obscureMode = OBSCURE_MODE_PIXELATE;
private boolean doTweening = true;
public boolean isDoTweening() {
return doTweening;
}
public void setDoTweening(boolean doTweening) {
this.doTweening = doTweening;
}
public String getObscureMode() {
return obscureMode;
}
public void setObscureMode(String obscureMode) {
this.obscureMode = obscureMode;
}
public RegionTrail (int startTime, int endTime)
{
this.startTime = startTime;
this.endTime = endTime;
}
public int getStartTime() {
return startTime;
}
public void setStartTime(int startTime) {
this.startTime = startTime;
}
public int getEndTime() {
return endTime;
}
public void setEndTime(int endTime) {
this.endTime = endTime;
}
public void addRegion (ObscureRegion or)
{
regionMap.put(or.timeStamp,or);
or.setRegionTrail(this);
}
public void removeRegion (ObscureRegion or)
{
regionMap.remove(or.timeStamp);
}
public Iterator<ObscureRegion> getRegionsIterator ()
{
return regionMap.values().iterator();
}
public ObscureRegion getRegion (Integer key)
{
return regionMap.get(key);
}
public TreeSet<Integer> getRegionKeys ()
{
TreeSet<Integer> regionKeys = new TreeSet<Integer>(regionMap.keySet());
return regionKeys;
}
public boolean isWithinTime (int time)
{
if (time < startTime || time > endTime)
return false;
else
return true;
}
public ObscureRegion getCurrentRegion (int time, boolean doTween)
{
ObscureRegion regionResult = null;
if (time < startTime || time > endTime)
return null;
else if (regionMap.size() > 0)
{
TreeSet<Integer> regionKeys = new TreeSet<Integer>(regionMap.keySet());
Integer lastRegionKey = -1, regionKey = -1;
Iterator<Integer> itKeys = regionKeys.iterator();
while (itKeys.hasNext())
{
regionKey = itKeys.next();
int comp = regionKey.compareTo(time);
if (comp == 0 || comp == 1)
{
ObscureRegion regionThis = regionMap.get(regionKey);
if (lastRegionKey != -1 && doTween)
{
ObscureRegion regionLast = regionMap.get(lastRegionKey);
float sx, sy, ex, ey;
int timeDiff = regionThis.timeStamp - regionLast.timeStamp;
int timePassed = time - regionLast.timeStamp;
float d = ((float)timePassed) / ((float)timeDiff);
sx = regionLast.sx + ((regionThis.sx-regionLast.sx)*d);
sy = regionLast.sy + ((regionThis.sy-regionLast.sy)*d);
ex = regionLast.ex + ((regionThis.ex-regionLast.ex)*d);
ey = regionLast.ey + ((regionThis.ey-regionLast.ey)*d);
regionResult = new ObscureRegion(time, sx, sy, ex, ey);
}
else
regionResult = regionThis;
break; //it is a match!
}
lastRegionKey = regionKey;
}
if (regionResult == null)
regionResult = regionMap.get(lastRegionKey);
}
return regionResult;
}
}
ObscureRegion.java
public class ObscureRegion {
/*
* Thinking about whether or not a region should contain multiple start/end times
* realizing that doing this would make editing a real pita
* Of course, it would make displaying be a 1000x better though.
class PositionTime {
int sx = 0;
int sy = 0;
int ex = 0;
int ey = 0;
int startTime = 0;
int endTime = 0;
PositionTime(int _sx, int _sy, int _ex, int _ey, int _startTime, int _endTime) {
}
}
*/
public static final float DEFAULT_X_SIZE = 150;
public static final float DEFAULT_Y_SIZE = 150;
public float sx = 0;
public float sy = 0;
public float ex = 0;
public float ey = 0;
public int timeStamp = 0;
public RegionTrail regionTrail;
private RectF rectF;
public ObscureRegion(int _timeStamp, float _sx, float _sy, float _ex, float _ey) {
timeStamp = _timeStamp;
sx = _sx;
sy = _sy;
ex = _ex;
ey = _ey;
if (sx < 0) {
sx = 0;
} else if (sy < 0) {
sy = 0;
}
}
public ObscureRegion(int _startTime, float _sx, float _sy) {
this(_startTime, _sx - DEFAULT_X_SIZE/2, _sy - DEFAULT_Y_SIZE/2, _sx + DEFAULT_X_SIZE/2, _sy + DEFAULT_Y_SIZE/2);
}
public void moveRegion(float _sx, float _sy) {
moveRegion(_sx - DEFAULT_X_SIZE/2, _sy - DEFAULT_Y_SIZE/2, _sx + DEFAULT_X_SIZE/2, _sy + DEFAULT_Y_SIZE/2);
}
public void moveRegion(float _sx, float _sy, float _ex, float _ey) {
sx = _sx;
sy = _sy;
ex = _ex;
ey = _ey;
rectF = null;
}
public RectF getRectF() {
if (rectF == null)
rectF = new RectF(sx, sy, ex, ey);
return rectF;
}
public RectF getBounds() {
return getRectF();
}
public String getStringData(float widthMod, float heightMod, int startTime, int duration, String currentMode) {
//left, right, top, bottom
return "" + (float)startTime/(float)1000 + ',' + (float)(startTime+duration)/(float)1000 + ',' + (int)(sx*widthMod) + ',' + (int)(ex*widthMod) + ',' + (int)(sy*heightMod) + ',' + (int)(ey*heightMod) + ',' + currentMode;
}
public RegionTrail getRegionTrail() {
return regionTrail;
}
public void setRegionTrail(RegionTrail regionTrail) {
this.regionTrail = regionTrail;
}
}
FFMPEGWrapper.java
public class FFMPEGWrapper {
String[] libraryAssets = {"ffmpeg"};
public File fileBinDir;
Context context;
private final static String FFMPEG_BINARY_VERSION = "0.10.4.1";
private final static String FFMPEG_VERSION_KEY = "ffmpegkey";
public FFMPEGWrapper(Context _context) throws FileNotFoundException, IOException {
context = _context;
fileBinDir = context.getDir("bin",0);
checkBinary();
}
private void checkBinary () throws FileNotFoundException, IOException
{
SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
String currTorBinary = prefs.getString(FFMPEG_VERSION_KEY, null);
if ((currTorBinary == null || (!currTorBinary.equals(FFMPEG_BINARY_VERSION)))
|| !new File(fileBinDir,libraryAssets[0]).exists())
{
BinaryInstaller bi = new BinaryInstaller(context,fileBinDir);
bi.installFromRaw();
}
}
public void execProcess( String[] cmds, ShellCallback sc) throws Exception {
ProcessBuilder pb = new ProcessBuilder(cmds);
pb.redirectErrorStream(true);
Process process = pb.start();
BufferedReader reader = new BufferedReader(new InputStreamReader(process.getInputStream()));
String line;
/*switch(command_call_type)
{
case Keys.KEY_COMMANDEXE_TYPE_MERGEFRAME:
// refincereference.updateLoadingbar(30);
break;
}*/
while ((line = reader.readLine()) != null)
{
if (sc != null)
{
sc.shellOut(line.toCharArray());
Log.d("FFMPEG", line.toCharArray()+"");
}
}
/*switch(command_call_type)
{
case Keys.KEY_COMMANDEXE_TYPE_MERGEFRAME:
//refincereference.updateLoadingbar(40);
break;
case Keys.KEY_COMMANDEXE_TYPE_CLIPMP3:
//refincereference.updateLoadingbar(60);
break;
case Keys.KEY_COMMANDEXE_TYPE_MP3TOM4A:
//refincereference.updateLoadingbar(80);
break;
}*/
/*
if (process != null) {
process.destroy();
}*/
}
public class FFMPEGArg
{
String key;
String value;
public static final String ARG_VIDEOCODEC = "vcodec";
public static final String ARG_VERBOSITY = "v";
public static final String ARG_FILE_INPUT = "i";
public static final String ARG_SIZE = "-s";
public static final String ARG_FRAMERATE = "-r";
public static final String ARG_FORMAT = "-f";
}
public void processVideo(File redactSettingsFile,
ArrayList<RegionTrail> obscureRegionTrails, File inputFile, File outputFile, String format, int mDuration,
int iWidth, int iHeight, int oWidth, int oHeight, int frameRate, int kbitRate, String vcodec, String acodec, ShellCallback sc) throws Exception {
float widthMod = ((float)oWidth)/((float)iWidth);
float heightMod = ((float)oHeight)/((float)iHeight);
writeRedactData(redactSettingsFile, obscureRegionTrails, widthMod, heightMod, mDuration);
if (vcodec == null)
vcodec = "copy";//"libx264"
if (acodec == null)
acodec = "copy";
String ffmpegBin = new File(fileBinDir,"ffmpeg").getAbsolutePath();
Runtime.getRuntime().exec("chmod 700 " +ffmpegBin);
String[] ffmpegCommand=new String[]{
ffmpegBin, "-h"
};
/* String[] ffmpegCommand = {ffmpegBin, "-y", "-i", inputFile.getPath(),
"-vcodec", vcodec,
"-b", kbitRate+"k",
"-s", oWidth + "x" + oHeight,
"-r", ""+frameRate,
"-acodec", acodec,
"-f", format,
"-vf","redact=" + redactSettingsFile.getAbsolutePath(),
outputFile.getPath()};*/
//./ffmpeg -y -i test.mp4 -vframes 999999 -vf 'redact=blurbox.txt [out] [d], [d]nullsink' -acodec copy outputa.mp4
//ffmpeg -v 10 -y -i /sdcard/org.witness.sscvideoproto/videocapture1042744151.mp4 -vcodec libx264
//-b 3000k -s 720x480 -r 30 -acodec copy -f mp4 -vf 'redact=/data/data/org.witness.sscvideoproto/redact_unsort.txt'
///sdcard/org.witness.sscvideoproto/new.mp4
//"-vf" , "redact=" + Utils.getAvailiableStorageLocation() + "/" + PACKAGENAME + "/redact_unsort.txt",
// Need to make sure this will create a legitimate mp4 file
//"-acodec", "ac3", "-ac", "1", "-ar", "16000", "-ab", "32k",
/*
String[] ffmpegCommand = {"/data/data/"+PACKAGENAME+"/ffmpeg", "-v", "10", "-y", "-i", recordingFile.getPath(),
"-vcodec", "libx264", "-b", "3000k", "-vpre", "baseline", "-s", "720x480", "-r", "30",
//"-vf", "drawbox=10:20:200:60:red@0.5",
"-vf" , "\"movie="+ overlayImage.getPath() +" [logo];[in][logo] overlay=0:0 [out]\"",
"-acodec", "copy",
"-f", "mp4", savePath.getPath()+"/output.mp4"};
*/
// execProcess(ffmpegCommand, sc);
}
private void writeRedactData(File redactSettingsFile, ArrayList<RegionTrail> regionTrails, float widthMod, float heightMod, int mDuration) throws IOException {
// Write out the finger data
FileWriter redactSettingsFileWriter = new FileWriter(redactSettingsFile);
PrintWriter redactSettingsPrintWriter = new PrintWriter(redactSettingsFileWriter);
ObscureRegion or = null, lastOr = null;
String orData = "";
for (RegionTrail trail : regionTrails)
{
if (trail.isDoTweening())
{
int timeInc = 100;
for (int i = 0; i < mDuration; i = i+timeInc)
{
or = trail.getCurrentRegion(i, trail.isDoTweening());
if (or != null)
{
orData = or.getStringData(widthMod, heightMod,i,timeInc, trail.getObscureMode());
redactSettingsPrintWriter.println(orData);
}
}
}
else
{
for (Integer orKey : trail.getRegionKeys())
{
or = trail.getRegion(orKey);
if (lastOr != null)
{
orData = lastOr.getStringData(widthMod, heightMod,or.timeStamp,or.timeStamp-lastOr.timeStamp, trail.getObscureMode());
}
redactSettingsPrintWriter.println(orData);
lastOr = or;
}
if (or != null)
{
orData = lastOr.getStringData(widthMod, heightMod,or.timeStamp,or.timeStamp-lastOr.timeStamp, trail.getObscureMode());
redactSettingsPrintWriter.println(orData);
}
}
}
redactSettingsPrintWriter.flush();
redactSettingsPrintWriter.close();
}
class FileMover {
InputStream inputStream;
File destination;
public FileMover(InputStream _inputStream, File _destination) {
inputStream = _inputStream;
destination = _destination;
}
public void moveIt() throws IOException {
OutputStream destinationOut = new BufferedOutputStream(new FileOutputStream(destination));
int numRead;
byte[] buf = new byte[1024];
while ((numRead = inputStream.read(buf) ) >= 0) {
destinationOut.write(buf, 0, numRead);
}
destinationOut.flush();
destinationOut.close();
}
}
}
BinaryInstaller.java
public class BinaryInstaller {
File installFolder;
Context context;
private static int isARMv6 = -1;
private static String CHMOD_EXEC = "700";
private final static int FILE_WRITE_BUFFER_SIZE = 32256;
public BinaryInstaller (Context context, File installFolder)
{
this.installFolder = installFolder;
this.context = context;
}
//
/*
* Extract the Tor binary from the APK file using ZIP
*/
public boolean installFromRaw () throws IOException, FileNotFoundException
{
InputStream is;
File outFile;
is = context.getResources().openRawResource(R.raw.ffmpeg);
outFile = new File(installFolder, "ffmpeg");
streamToFile(is, outFile, false, false, "700");
return true;
}
private static void copyAssetFile(Context ctx, String asset, File file) throws IOException, InterruptedException
{
DataOutputStream out = new DataOutputStream(new FileOutputStream(file));
InputStream is = new GZIPInputStream(ctx.getAssets().open(asset));
byte buf[] = new byte[8172];
int len;
while ((len = is.read(buf)) > 0) {
out.write(buf, 0, len);
}
out.close();
is.close();
}
/*
* Write the inputstream contents to the file
*/
private static boolean streamToFile(InputStream stm, File outFile, boolean append, boolean zip, String mode) throws IOException
{
byte[] buffer = new byte[FILE_WRITE_BUFFER_SIZE];
int bytecount;
OutputStream stmOut = new FileOutputStream(outFile, append);
if (zip)
{
ZipInputStream zis = new ZipInputStream(stm);
ZipEntry ze = zis.getNextEntry();
stm = zis;
}
while ((bytecount = stm.read(buffer)) > 0)
{
stmOut.write(buffer, 0, bytecount);
}
stmOut.close();
stm.close();
Runtime.getRuntime().exec("chmod "+mode+" "+outFile.getAbsolutePath());
return true;
}
//copy the file from inputstream to File output - alternative impl
public void copyFile (InputStream is, File outputFile)
{
try {
outputFile.createNewFile();
DataOutputStream out = new DataOutputStream(new FileOutputStream(outputFile));
DataInputStream in = new DataInputStream(is);
int b = -1;
byte[] data = new byte[1024];
while ((b = in.read(data)) != -1) {
out.write(data);
}
if (b == -1); //rejoice
//
out.flush();
out.close();
in.close();
// chmod?
} catch (IOException ex) {
Log.e("SLIDEAGRAM", "error copying binary", ex);
}
}
/**
* Check if this is an ARMv6 device
* @return true if this is ARMv6
*/
private static boolean isARMv6() {
if (isARMv6 == -1) {
BufferedReader r = null;
try {
isARMv6 = 0;
r = new BufferedReader(new FileReader("/proc/cpuinfo"));
for (String line = r.readLine(); line != null; line = r.readLine()) {
if (line.startsWith("Processor") && line.contains("ARMv6")) {
isARMv6 = 1;
break;
} else if (line.startsWith("CPU architecture") && (line.contains("6TE") || line.contains("5TE"))) {
isARMv6 = 1;
break;
}
}
} catch (Exception ex) {
} finally {
if (r != null) try {r.close();} catch (Exception ex) {}
}
}
return (isARMv6 == 1);
}
private static void copyRawFile(Context ctx, int resid, File file, String mode, boolean isZipd) throws IOException, InterruptedException
{
final String abspath = file.getAbsolutePath();
// Write the iptables binary
final FileOutputStream out = new FileOutputStream(file);
InputStream is = ctx.getResources().openRawResource(resid);
if (isZipd)
{
ZipInputStream zis = new ZipInputStream(is);
ZipEntry ze = zis.getNextEntry();
is = zis;
}
byte buf[] = new byte[1024];
int len;
while ((len = is.read(buf)) > 0) {
out.write(buf, 0, len);
}
out.close();
is.close();
// Change the permissions
Runtime.getRuntime().exec("chmod "+mode+" "+abspath).waitFor();
}
}
FFMpegVideoProcess.java
public class FFMpegVideoProcess
{
public static void mergeFramesIntoVideo(Activity context,String duration_per_frame,String input_frame_path,String out_video_path)throws Exception
{
//Looper.prepare();
String ffmpegBin;
FFMPEGWrapper ffmpeg = null;
ShellUtils.ShellCallback sc;
if (ffmpeg == null)
ffmpeg = new FFMPEGWrapper(context);
sc = new ShellUtils.ShellCallback ()
{
int total = 0;
int current = 0;
@Override
public void shellOut(char[] shellout) {
String line = new String(shellout);
int idx1;
String newStatus = null;
int progress = 0;
if ((idx1 = line.indexOf("Duration:"))!=-1)
{
int idx2 = line.indexOf(",", idx1);
String time = line.substring(idx1+10,idx2);
int hour = Integer.parseInt(time.substring(0,2));
int min = Integer.parseInt(time.substring(3,5));
int sec = Integer.parseInt(time.substring(6,8));
total = (hour * 60 * 60) + (min * 60) + sec;
newStatus = line;
progress = 0;
}
else if ((idx1 = line.indexOf("time="))!=-1)
{
int idx2 = line.indexOf(" ", idx1);
String time = line.substring(idx1+5,idx2);
newStatus = line;
int hour = Integer.parseInt(time.substring(0,2));
int min = Integer.parseInt(time.substring(3,5));
int sec = Integer.parseInt(time.substring(6,8));
current = (hour * 60 * 60) + (min * 60) + sec;
progress = (int)( ((float)current) / ((float)total) *100f );
}
if (newStatus != null)
{
// Message msg = mHandler.obtainMessage(1);
// msg.getData().putInt("progress", progress);
// msg.getData().putString("status", newStatus);
// mHandler.sendMessage(msg);
}
}
};
ffmpegBin = new File(ffmpeg.fileBinDir,"ffmpeg").getAbsolutePath();
Runtime.getRuntime().exec("chmod 700 " +ffmpegBin);
// refincereference.updateLoadingbar(20);
ffmpeg.execProcess(new String[]{
ffmpegBin,
"-f",
"image2",
"-r",
duration_per_frame,
"-i",
input_frame_path,
"-s",
"640x640",
//"640x388",
"-vcodec",
"libx264",
"-y",
out_video_path
},sc);
//Looper.loop();
}
}
将所有文件放在一起后，如果您想将帧合并到视频中，请调用此函数，如下所示
FFMpegVideoProcess.createFramesinFolder(this,DIR_IN_WHICH_YOU_WANT_TO_KEEP_FRAMES, "frame_%03d.jpg");
FFMpegVideoProcess.mergeFramesIntoVideo(args1,DIR_IN_WHICH_YOU_WANT_TO_KEEP_FRAMES/frame_%3d.jpg",argN...);
如果您有任何疑问，请随时提问。谢谢
【讨论】：
如果没有有效的包装器/不满足您的要求，您可以创建一个描述应用程序需求的高级 C API（而不是为 Java 提供完整的 ffmpeg API），然后实现该 API ，即大部分功能，在 C/C++ 中使用 C 调用 ffmpeg API。
这种方法可能比为 ffmpeg 创建完整包装器更简单
【讨论】：