android.media.MediaExtractor Sample Flags

Question

What is the meaning of :

1. SAMPLE_FLAG_SYNC
2. SAMPLE_FLAG_ENCRYPTED

I have a difficulty understanding "sample in sync" concept of audio files.

Also, feel free to suggest any technical reference to understand the 'whole scene'.

Answer 1

SAMPLE_FLAG_SYNC - means extractor emit I-frame or key frame, decoder can start decoding only from key frame. more info on frame tipes here: http://en.wikipedia.org/wiki/Video_compression_picture_types

SAMPLE_FLAG_ENCRYPTED - when file\video is encrypted like DRM or so, then extractor can parse headers and emit encrypted frames, decoder or next component after exctractor should know how to decrypt it. this is rather long story how to make everything secure, for example it is discussed there: Playing encrypted video