我在

Android中使用

ExoPlayer,我正在尝试重现本地存储的加密视频.

ExoPlayer的模块化允许创建可以注入到ExoPlayer中的自定义组件,这种情况似乎如此.事实上,经过一些研究,我意识到,为了完成任务,我可以创建一个自定义的DataSource并覆盖open(),read()和close().

我也发现了this solution,但实际上这里整个文件是一步解密并存储在一个清晰的输入流中.这在很多情况下可以很好.但是如果我需要重现大文件怎么办？

所以问题是：如何在ExoPlayer中复制加密的视频,“即时”解密内容(不解密整个文件)？这可能吗

我尝试创建一个具有open()方法的自定义DataSource：

@Override

public long open(DataSpec dataSpec) throws FileDataSourceException {

try {

File file = new File(dataSpec.uri.getPath());

clearInputStream = new CipherInputStream(new FileInputStream(file), mCipher);

long skipped = clearInputStream.skip(dataSpec.position);

if (skipped < dataSpec.position) {

throw new EOFException();

}

if (dataSpec.length != C.LENGTH_UNBOUNDED) {

bytesRemaining = dataSpec.length;

} else {

bytesRemaining = clearInputStream.available();

if (bytesRemaining == 0) {

bytesRemaining = C.LENGTH_UNBOUNDED;

}

}

} catch (EOFException e) {

e.printStackTrace();

} catch (IOException e) {

e.printStackTrace();

}

opened = true;

if (listener != null) {

listener.onTransferStart();

}

return bytesRemaining;

}

这是read()方法：

@Override

public int read(byte[] buffer, int offset, int readLength) throws FileDataSourceException {

if (bytesRemaining == 0) {

return -1;

} else {

int bytesRead = 0;

int bytesToRead = bytesRemaining == C.LENGTH_UNBOUNDED ? readLength

: (int) Math.min(bytesRemaining, readLength);

try {

bytesRead = clearInputStream.read(buffer, offset, bytesToRead);

} catch (IOException e) {

e.printStackTrace();

}

if (bytesRead > 0) {

if (bytesRemaining != C.LENGTH_UNBOUNDED) {

bytesRemaining -= bytesRead;

}

if (listener != null) {

listener.onBytesTransferred(bytesRead);

}

}

return bytesRead;

}

}

如果不是编码文件,我传递一个清除文件,只是删除CipherInputStream部分,那么它工作正常,而是加密文件我得到这个错误：

Unexpected exception loading stream

java.lang.IllegalStateException: Top bit not zero: -1195853062

at com.google.android.exoplayer.util.ParsableByteArray.readUnsignedIntToInt(ParsableByteArray.java:240)

at com.google.android.exoplayer.extractor.mp4.Mp4Extractor.readSample(Mp4Extractor.java:331)

at com.google.android.exoplayer.extractor.mp4.Mp4Extractor.read(Mp4Extractor.java:122)

at com.google.android.exoplayer.extractor.ExtractorSampleSource$ExtractingLoadable.load(ExtractorSampleSource.java:745)

at com.google.android.exoplayer.upstream.Loader$LoadTask.run(Loader.java:209)

at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:423)

at java.util.concurrent.FutureTask.run(FutureTask.java:237)

at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)

at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)

at java.lang.Thread.run(Thread.java:818)

编辑：

以这种方式生成加密视频：

Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");

SecretKeySpec keySpec = new SecretKeySpec("0123456789012345".getBytes(), "AES");

IvParameterSpec ivSpec = new IvParameterSpec("0123459876543210".getBytes());

cipher.init(Cipher.ENCRYPT_MODE, keySpec, ivSpec);

outputStream = new CipherOutputStream(output_stream, cipher);

然后将outputStream保存到文件中.