Amazon Kinesis Video Streams Parser Library

License

This library is licensed under the Apache 2.0 License.

Introduction

The Amazon Kinesis Video Streams Parser Library for Java enables Java developers to parse the streams returned by GetMedia calls to Amazon Kinesis Video. It contains:

• A streaming Mkv Parser called StreamingMkvReader that provides an iterative interface to read the MkvElements in a stream.
• Applications such as OutputSegmentMerger and FragmentMetadataVisitor built using the StreamingMkvReader .
• A callback based parser called EBMLParser that minimizes data buffering and copying. StreamingMkvReader is built on top of EBMLParser
• Unit tests for the applications and parsers that demonstrate how the applications work.

Building from Source

After you've downloaded the code from GitHub, you can build it using Maven. Use this command: mvn clean install

Details

StreamingMkvReader

StreamingMkvReader which provides an iterative interface to read MkvElements from a stream. A caller calls nextIfAvailable to get the next MkvElement. An MkvElement wrapped in an Optional is returned if a complete element is available. It buffers an individual MkvElement until it can return a complete MkvElement.
The mightHaveNext method returns true if there is a chance that additional MkvElements can be returned. It returns false when the end of the input stream has been reached.

MkvElement

There are three types of MkvElement vended by a MkvStreamReader:

• MkvDataElement: This encapsulates Mkv Elements that are not master elements and contain data.
• MkvStartMasterElement : This represents the start of a master Mkv element that contains child elements. Child elements can be other master elements or data elements.
• MkvEndMasterElement : This represents the end of master element that contains child elements.

MkvElementVisitor

The MkvElementVisitor is a visitor pattern that helps process the events in the MkvElement hierarchy. It has a visit method for each type of MkvElement.

Visitors

A GetMedia call to Kinesis Video vends a stream of fragments where each fragment is encapsulated in a Mkv stream containing EBML and Segment elements. OutputSegmentMerger can be used to merge consecutive fragments that share the same EBML and Track data into a single Mkv stream with a shared EBML and Segment. This is useful for passing the output of GetMedia to any downstream processor that expects a single Mkv stream with one Segment. Its use can be seen in OutputSegmentMergerTest

FragmentMetadataVisitor is a MkvElementVisitor that collects the Kinesis Video specific meta-data (such as FragmentNumber and Server Side Timestamp ) for the current fragment being processed. The getCurrentFragmentMetadata method can be used to get the current fragment's metadata. Similarly getPreviousFragmentMetadata can be used get the previous fragment's metadata. The getMkvTrackMetadata method can be used to get the details of a particular track.

ElementSizeAndOffsetVisitor is a visitor that writes out the metadata of the Mkv elements in a stream. For each element the name, offset, header size and data size is written out. The output uses indentation to indicate the hierarchy of master elements and their child elements. ElementSizeAndOffsetVisitor is useful for looking into Mkv streams, where mkvinfo fails.

CountVisitor is a visitor that can be used to count the number of Mkv elements of different types in a Mkv stream.

CompositeMkvElementVisitor is a visitor that is made up of a number of constituent visitors. It calls accept on the visited MkvElement for each constituent visitor in the order in which the visitors are specified.

Release Notes

Release 1.0.0 (November 2017)

• First release of the Amazon Kinesis Video Parser Library.
• Supports Mkv elements up to version 4.
• Known issues:
  • EBMLMaxIDLength and EBMLMaxSizeLength are hardcoded as 4 and 8 bytes respectively
  • Unknown EBML elements not specified in MkvTypeInfos are not readable by the user using StreamingMkvReader.
  • Unknown EBML elements not specified in MkvTypeInfos of unknown length lead to an exception.
  • Does not do any CRC validation for any Mkv elements with the CRC-32 element.