Embedding Custom Meta-Data (Bounding Boxes) into HLS Video Streams
Introduction
This article explores techniques for embedding custom meta-data, specifically bounding boxes, into HLS video streams. Bounding boxes can provide valuable information for applications such as object detection, tracking, and video analytics.
HLS (HTTP Live Streaming) and Meta-Data
HLS is a widely used streaming protocol for delivering video content over the internet. HLS allows for the inclusion of meta-data within the video stream, enabling the transmission of additional information along with the video data.
Embedding Bounding Boxes
There are several approaches to embed bounding box information into an HLS stream:
1. ID3 Tags
- ID3 tags are commonly used for embedding meta-data into MP4 files.
- We can utilize ID3 tags to store bounding box coordinates in the video stream’s MP4 segments.
Example:
<ID3> <TXXX> <TIT2>Bounding Box Information</TIT2> <TXXX>x1,y1,x2,y2</TXXX> </TXXX> </ID3>
2. MPEG-TS (Transport Stream) Packets
- MPEG-TS packets form the basis of HLS streams.
- Custom meta-data, including bounding boxes, can be encapsulated within these packets.
Example:
0x47 // Start of a private section 0x40 // Section length 0x10 // Table ID (private data) 0x00 // Version number 0x00 // Current next indicator 0x01 // Section number 0x01 // Last section number // ... data payload containing bounding boxes ...
3. Custom Segment Meta-Data
- HLS playlists can include custom meta-data files alongside each video segment.
- These files can store JSON or XML data, including bounding box coordinates.
Example:
| Segment | Meta-Data File |
|---|---|
| segment_1.ts | segment_1.json |
| segment_2.ts | segment_2.json |
{ "bounding_boxes": [ { "x1": 100, "y1": 200, "x2": 300, "y2": 400 }, { "x1": 500, "y1": 100, "x2": 700, "y2": 300 } ] }
Decoding and Using Bounding Box Data
The embedded bounding box data needs to be decoded and utilized on the client-side, typically by a video player or an application that consumes the stream.
- ID3 tags can be parsed using libraries like getID3.
- MPEG-TS packets need to be demultiplexed and parsed for custom meta-data.
- Custom segment meta-data can be accessed and parsed using JavaScript or other scripting languages.
Tools and Libraries
Various tools and libraries can aid in the embedding and decoding of bounding boxes in HLS streams:
- FFmpeg: For encoding and manipulating video streams, including meta-data embedding.
- libav: A multimedia library for processing video and audio, providing functions for working with MPEG-TS packets.
- HLS.js: A JavaScript library for playing HLS streams and managing meta-data.
Conclusion
Embedding custom meta-data like bounding boxes into HLS video streams offers a powerful way to enhance video analytics, object detection, and other applications. By leveraging techniques like ID3 tags, MPEG-TS packets, and custom segment meta-data, we can seamlessly integrate valuable information within video streams, enabling real-time processing and analysis.