What is video manifest?

A video manifest plays a crucial role in modern video streaming, particularly in delivering video content over the internet using adaptive bitrate streaming (ABR). ABR is an essential technology that allows video players to dynamically adjust video quality based on the viewer's network conditions, thus offering a smooth and uninterrupted viewing experience.

In this detailed discussion, we’ll dive into what a video manifest is, its importance in the video delivery ecosystem, and how it works across different adaptive streaming formats such as HLS (HTTP live streaming) and DASH (Dynamic adaptive streaming over HTTP). We’ll also explore the significance of video manifests in content delivery, the challenges they address, and their broader impact on the video industry.

‍

What is a video manifest?

A video manifest is essentially a file or a set of instructions that describe how a video stream is structured, where the video segments (small chunks of the video) are located, and how they should be played back. It serves as a roadmap for video players, enabling them to download, buffer, and render video content in the correct order and at the right quality.

There are two major types of video manifests used in the context of adaptive streaming. Both serve a similar purpose but are tailored to different streaming technologies.

1. HLS video manifest (M3U8 file)
2. DASH video manifest (MPD file)
   ‍

‍

Why is video manifest important?

The role of the video manifest is critical in providing efficient, scalable, and adaptable video streaming. The video manifests solve several key challenges:

Network adaptation: Network conditions can fluctuate depending on a variety of factors, such as available bandwidth, signal strength (in mobile networks), or congestion. A video manifest contains multiple representations of the same video at different bitrates, resolutions, and quality levels. This allows the player to switch to a lower or higher quality stream based on the user’s real-time bandwidth, ensuring smooth playback without buffering or interruptions.

Content distribution: When videos are distributed over content delivery networks (CDNs), they are broken down into smaller segments to optimize delivery. These segments are referenced within the video manifest, which helps the player locate and download the correct parts of the video from servers closest to the viewer. This is especially important for large-scale streaming platforms like Netflix, YouTube, or live sports broadcasts.

Efficient playback: By defining the sequence and timing of video segments, a manifest ensures that video players can reconstruct the original video from individual parts. The manifest also includes metadata such as timing information, allowing seamless transitions between different segments.

Support for multiple devices: Modern video delivery needs to cater to a wide range of devices, each with different display capabilities and performance constraints. Manifests make it possible to deliver the most appropriate version of a video depending on the device – from mobile phones to 4K TVs.

‍

HLS video manifest (M3U8 Format)

HTTP live streaming (HLS) is a popular adaptive bitrate streaming protocol created by Apple. It is widely used for video delivery, particularly on Apple devices, but is supported on a range of other platforms and devices. HLS uses an M3U8 file as its video manifest. The M3U8 file is a variant of the M3U format, which is commonly used for playlists in media players. In the context of HLS, the M3U8 file serves as the index or playlist for the video stream.

‍

Structure of an HLS manifest

The HLS manifest contains a list of media segments, typically in .ts (MPEG-2 Transport Stream) format, and may include multiple bitrate versions of the video.

Here’s a simplified example of what an M3U8 manifest might look like:

1#EXTM3U
2#EXT-X-VERSION:3
3#EXT-X-STREAM-INF:BANDWIDTH=800000,RESOLUTION=640x360
4video_360p.m3u8
5#EXT-X-STREAM-INF:BANDWIDTH=1400000,RESOLUTION=1280x720
6video_720p.m3u8
7#EXT-X-STREAM-INF:BANDWIDTH=2800000,RESOLUTION=1920x1080
8video_1080p.m3u8

‍

This example manifest provides three different versions of the video, each at a different resolution and bitrate. The player will choose the appropriate stream based on the available network bandwidth.

The manifest points to separate M3U8 files (such as video_360p.m3u8), which in turn contain references to individual media segments. An example of a segment manifest could look like this:

‍

1#EXTM3U
2#EXT-X-TARGETDURATION:10
3#EXTINF:10.0,
4segment1.ts
5#EXTINF:10.0,
6segment2.ts
7#EXTINF:10.0,
8Segment3.ts

‍

In this case, the player will download and play each segment (segment1.ts, segment2.ts, etc.) sequentially.

Benefits of HLS and its manifest

• Adaptive streaming: The M3U8 manifest allows HLS to adaptively stream video content. The player can start at a low bitrate and seamlessly switch to a higher bitrate if bandwidth improves or vice versa if it degrades.
• Widespread support: HLS is supported on a wide range of devices, especially Apple products like iPhones, iPads, and Apple TVs. It is also compatible with web browsers and many Android devices.
• Resilience to network conditions: HLS allows for robust streaming even in suboptimal network conditions. The manifest helps guide the player in switching between different quality levels in real time.
  ‍

‍

DASH video manifest (MPD format)

Dynamic Adaptive Streaming over HTTP (DASH) is another adaptive streaming protocol, and unlike HLS, it is an open standard that is not tied to a specific ecosystem or device manufacturer. DASH uses MPD (Media Presentation Description) files as video manifests.

‍

Structure of a DASH manifest

The MPD file contains a list of representations, which are the different versions of the video at various bitrates, resolutions, or frame rates. Each representation points to media segments in ISO base Media File Format (MP4) or other container formats.

A simple example of a DASH manifest might look like this:

1<MPD xmlns="urn:mpeg:DASH:schema:MPD:2011" minBufferTime="PT1.5S" type="static" mediaPresentationDuration="PT0H4M40.52S" maxSegmentDuration="PT2S" profiles="urn:mpeg:dash:profile:isoff-live:2011">
2  <Period>
3    <AdaptationSet mimeType="video/mp4" segmentAlignment="true">
4      <Representation id="video_360p" bandwidth="800000" width="640" height="360">
5        <SegmentTemplate timescale="1000" initialization="video_360p_init.mp4" media="video_360p_$Number$.mp4" startNumber="1"/>
6      </Representation>
7      <Representation id="video_720p" bandwidth="1400000" width="1280" height="720">
8        <SegmentTemplate timescale="1000" initialization="video_720p_init.mp4" media="video_720p_$Number$.mp4" startNumber="1"/>
9      </Representation>
10    </AdaptationSet>
11  </Period>
12</MPD>

‍

In this example, the MPD manifest contains two representations of the video (360p and 720p), and each representation has a SegmentTemplate. The SegmentTemplate defines the location of video segments, which can then be requested by the player.

‍

Benefits of DASH and its manifest

• Open standard: DASH is an open protocol and not tied to any specific platform orcompany, unlike HLS, which was developed by Apple. This makes DASH moreflexible and widely adopted across different devices and platforms.
• Adaptability: Just like HLS, DASH allows for adaptive streaming. The player canswitch between different representations (bitrate and resolution levels)depending on the viewer's network conditions.
• Efficient segment management: The MPD manifest efficiently handles different segment formats and codecs and supports multiple tracks (such as audio and subtitles) in addition to video streams.

‍

The role of CDNs in manifest-based streaming

In both HLS and DASH, CDNs play an important role in delivering video content efficiently to users worldwide. CDNs store copies of video segments across distributed servers, allowing users to download content from a nearby server, which helps reduce latency and buffering.

‍

‍

The video manifest enables the player to request the appropriate segments from the CDN. For instance, if the network is congested, the player may request a low-bitrate segment, and the CDN will provide that segment from its nearest server.
‍

Challenges and limitations of video manifests

• Latency: In live streaming scenarios, video manifests must be frequently updated to include new segments. This can introduce some latency between the actual event and what the viewer sees.
• Compatibility: While HLS is widely supported, DASH may not work on certain devices, particularly older or proprietary platforms that favor HLS. This means content providers often must maintain multiple manifest formats for compatibility.
• Encryption and DRM: Both HLS and DASH support encryption and digital rights management (DRM) to protect content from unauthorized access. The manifest file must include references to encryption keys and DRM licenses, which can add complexity.
• Caching and efficiency: In cases where manifests change frequently (e.g., live streaming), caching these files effectively can be challenging. CDNs need to efficiently handle these updates without serving stale manifest.

‍

Real-time use cases for HLS

Here are real-time use cases and examples of HLS:

Apple keynote live streaming:

Use case: Apple uses HLS to stream its highly anticipated keynote events live to millions of viewers worldwide. These events, which include product launches and major announcements, are streamed in real-time using HLS, ensuring seamless delivery across all Apple devices.

Example: The Apple September 2023 Keynote, where the new iPhone and Apple Watch were launched, was streamed live using HLS. Apple devices dynamically adjust the video quality based on the viewer’s internet speed for uninterrupted viewing.
‍

Real-time sports streaming on ESPN+:

Use case: Sports streaming platforms, like ESPN+, use HLS to broadcast live games and events. Real-time delivery is crucial for sports content, and HLS’s adaptive streaming ensures that the stream quality adjusts dynamically to avoid buffering during crucial moments.

Example: During a live UFC fight, ESPN+ delivers real-time streaming through HLS, ensuring fans can watch high-quality, uninterrupted coverage, with quality switching based on their internet connection.
‍

Concerts and music festivals:

Use case: Platforms that stream live concerts and music festivals often rely on HLS to provide real-time video delivery to audiences globally.

Example: Coachella’s 2023 live stream used HLS to deliver real-time performances of artists to millions of viewers globally, providing adaptive streaming on mobile and desktop devices.

‍

Real-time use cases for DASH

Here are real-time use cases and examples of DASH:

Live streaming on YouTube:

Use case: YouTube Live uses DASH for real-time streaming, particularly for events that have a large audience, such as conferences, political events, and music performances. DASH enables adaptive streaming to devices with various network conditions, ensuring viewers receive the best possible quality.

Example: During the 2023 SpaceX Starship launch, YouTube delivered the event live using DASH. As millions of viewers tuned in from different devices, DASH ensured real-time streaming with high-quality video for users with strong internet connections while adjusting for those with lower bandwidth.

‍

Virtual events and webinars:

Use case: Real-time video conferencing platforms such as Zoom and Microsoft Teams utilize DASH for high-quality live streaming in large-scale webinars and virtual events. DASH supports adaptive streaming, helping these platforms manage varying network conditions of attendees.

Example: In real-time virtual events, like corporate town halls or live webinars hosted by Zoom, DASH enables high-quality streams with minimal latency. As participants join from different network environments, the platform adjusts the video quality in real-time.

‍

Real-time stock market streaming:

Use Case: Financial platforms use real-time streaming to broadcast stock market updates, news, and trading events. DASH allows these platforms to deliver live, low-latency video that is critical for making split-second trading decisions.

Example: Platforms like CNBC Pro use DASH for their real-time stock market streaming, providing live coverage of market movements and news. DASH ensures that financial professionals receive the most up-to-date information without delay.

‍

Conclusion

In adaptive streaming, the video manifest acts like a roadmap for playback. Whether it’s an M3U8 file for HLS or an MPD file for DASH (which streaming protocol is better anyway? Find out more ), the manifest helps deliver video streams smoothly and flexibly. This means you can enjoy a better viewing experience, even when your internet connection fluctuates.

And how do you deliver that smooth viewing experience to your audience? That’s where FastPix comes in. Our video API supports both video-on-demand and live streaming, offering features like adaptive bitrate streaming, multi-CDN delivery, and accelerated uploads. These tools work together to ensure your content streams flawlessly, providing your viewers with the reliable experience they crave, regardless of their connection.

Sign up today and give your audience the streaming quality they deserve!