get buffered data exoplayer

问题

I am not very experienced building Android apps and I am trying to make a small app using ExoPlayer. So hopefully you guys can pardon my ignorance. I am essentially trying to see if there is a way to get access to the buffered files. I searched around, but there doesn't seem to be an answer for this. I saw people talking about cacheDataSource, but then I thought, isn't the data already being cache by virtue of it buffering? For instance, when a video starts, it start buffering. I t continues to do so even if pause is pressed. If I am understanding this correctly, the video actually plays from the buffered data. I assume that this data must be stored somewhere. Is this cache data in this case? if not, then what is cache data? what is the difference here? and finally, how can I actually get access to whatever this is? I'v been trying to see where its being stored as and as what(meaning some kind of file may be), and I reached the DefaultAllocator class, which seems to have this line

availableAllocations[i] = new Allocation(initialAllocationBlock,allocationOffset);//is this it??

this is in the DefaultAllocator.java file. Not sure if im looking in the right place...

I am not able to make sense of what the buffer even is and how its stored. Youtube stores .exo files. I can see a cache folder in data/data/myAppName/cache by printing the getCacheDir(), but that seems to be giving out some java.io.fileAndSomeRandomChars. The buffer also gets deleted when the player is minimized or another app is opened.

Does the ExoPlayer also store files in chunks?

Any insight on this would be seriously super helpful!. Iv been stuck on this for a few days now. Super duper appreciate it!

回答1:

Buffers are not files, buffers are stored in application memory, and in this example they are instances of ByteBuffer class. ExoPlayer buffers are passed through instances of MediaCodecRenderer using processOutputBuffer() method.

Buffers are usually arrays of bytes or maybe some other kind of data, while ByteBuffer class adds some helpfull methods around it for tracking size of buffer ot its last accessed position using marker and so on.

The way how I access buffers is by extending the implementation of renderer that I am using and then override processOutputBuffer() like this:

public class CustomMediaCodecAudioRenderer extends MediaCodecAudioRenderer
{
     @Override
     protected boolean processOutputBuffer( long positionUs, long elapsedRealtimeUs, MediaCodec codec, ByteBuffer buffer, int bufferIndex, int bufferFlags, long bufferPresentationTimeUs, boolean shouldSkip ) throws ExoPlaybackException
     {

        boolean fullyProcessed;

        //Here you use the buffer
        doSomethingWithBuffer( buffer );


        //Here we allow renderer to do its normal stuff
        fullyProcessed = super.processOutputBuffer( positionUs,
            elapsedRealtimeUs,
            codec,
            buffer,
            bufferIndex,
            bufferFlags,
            bufferPresentationTimeUs,
            shouldSkip );





        return fullyProcessed;
    }

}

来源：https://stackoverflow.com/questions/43360227/get-buffered-data-exoplayer