H.265, also known as High Efficiency Video Coding (HEVC), is a video compression standard that was developed to improve upon the previous H.264 (AVC) standard. It offers more efficient compression, allowing for higher quality video at lower bit rates compared to its predecessor.
Some key features of H.265 include:
- Improved Compression: H.265 can achieve the same visual quality as H.264 while using roughly half the bit rate, making it a more efficient option for video compression.
- Support for Higher Resolution: It supports higher resolution video formats, including 4K and even 8K, making it suitable for ultra-high-definition content.
- Enhanced Parallel Processing: H.265 is designed to take advantage of modern hardware capabilities, allowing for better parallel processing and improved speed during video encoding and decoding.
Overall, H.265 is a significant advancement in video compression technology, offering higher efficiency and improved video quality, especially for high-resolution content. This makes it an important standard for various applications, including video streaming, broadcasting, surveillance, and more.
Can H.265 be used to stream live video to YouTube instead of H.264?
Technically, no, H.265 cannot be used to stream live video to YouTube when using the RTMP protocol. This limitation arises because the RTMP (Real-Time Messaging Protocol), which is commonly used for live streaming, supports only the H.264 codec for video compression.
Can H.265 be used on YouTube at all?
H.265 can be used for uploaded videos to YouTube since the platform supports decoding and processing H.265 content. However, for live streaming specifically, RTMP enforces the use of H.264.
What's H.264?
H.264, also known as Advanced Video Coding (AVC), is a widely used video compression standard that offers high-quality video at significantly lower bitrates compared to older formats. It is a popular choice for video streaming, recording, and broadcasting due to its efficiency and flexibility.
Key Features of H.264:
- High Compression Efficiency: H.264 reduces file sizes while maintaining video quality, making it ideal for streaming over the internet or storing large amounts of video data.
- Wide Compatibility: Supported by a vast range of devices, platforms, and applications, including Blu-ray players, streaming services, webcams, and video conferencing systems.
- Scalability: H.264 supports various resolutions, from low-quality mobile videos to high-definition (HD) and ultra-high-definition (UHD) formats.
- Error Resilience: Designed to maintain video playback quality even in networks with packet loss or variable bandwidth, ensuring smoother streaming.
- Flexible Profiles and Levels: H.264 offers multiple profiles (Baseline, Main, High, etc.) and levels to cater to diverse applications, from basic video conferencing to professional-grade broadcasting.
Applications of H.264:
- Streaming Services: Used by platforms like YouTube, Netflix, and Vimeo for delivering high-quality video over the internet.
- Surveillance Systems: Widely used in IP cameras for efficient video compression and storage.
- Video Conferencing: Powers real-time communication applications like Zoom, Microsoft Teams, and Skype.
- Broadcasting: Commonly adopted for TV broadcasting and Blu-ray content.
- Mobile Devices: Ensures efficient video playback and recording on smartphones and tablets.
H.264 remains one of the most reliable and versatile video codecs in use today, balancing quality and performance across various scenarios.
Why is H.264 required for RTMP streaming?
- RTMP Specification: RTMP, as defined by Adobe, was developed to support H.264 and AAC as the standard video and audio codecs. It does not include support for newer codecs like H.265 (HEVC).
- YouTube's Compatibility: YouTube's live streaming platform, which relies on RTMP for input streams, adheres to this standard, requiring video streams to use H.264 for compatibility.
Resolution: Encoding Up to 1080P
What’s the highest resolution supported by this HDMI codec?
Normally, for encoding, the HDMI codec supports a maximum resolution of 1920x1080P (commonly referred to as Full HD). This resolution ensures high-quality video encoding while maintaining compatibility with most streaming and display platforms.
Why is it limited to 1080P?
- Hardware Constraints: The codec's internal processing hardware is optimized for Full HD encoding to balance performance, power consumption, and efficiency.
- Streaming Protocols: Many streaming protocols and platforms prioritize 1080P as a standard for live streaming due to its widespread support and efficient bandwidth usage.
What’s the highest resolution for the decoding channel supported by this HDMI codec?
The HDMI codec supports 1CH 4K RTSP stream as the highest resolution for decoding input. However, there are certain limitations to consider:
Key Details:
1. Decoding Input:
- If a 1CH 4K RTSP stream is used for decoding, additional decoding input channels will not be available.
- The codec can handle only one 4K decoding input at a time due to hardware limitations.
2. Encoding Resolution:
- Even when the codec is decoding a 4K RTSP input stream, the maximum encoding resolution remains 1920x1080P (Full HD).
Applications:
- Single 4K Decoding Use Case: Ideal for scenarios requiring a single high-resolution input, such as surveillance or displaying a 4K RTSP stream from a camera or media source.
- Combined Encoding/Decoding: When both encoding and decoding are used simultaneously, the resolution and channel capabilities are optimized for Full HD encoding alongside the decoding tasks.
Bitrate mode: CBR/VBR
Does the HDMI codec support different bitrate control modes?
Yes, the HDMI codec supports both CBR (Constant Bitrate) and VBR (Variable Bitrate) modes.
Key Features:
1. CBR (Constant Bitrate):
- Maintains a consistent bitrate throughout the video stream.
- Ideal for environments with limited bandwidth or for ensuring stable network transmission.
- Ensures predictable network performance and reduces the risk of buffering issues.
2. VBR (Variable Bitrate):
- Adjusts the bitrate dynamically based on the complexity of the video content.
- Delivers better video quality for the same file size compared to CBR.
- Suitable for scenarios where video quality is prioritized and bandwidth is more flexible.
Applications:
- Use CBR for live streaming over constrained or inconsistent network conditions to minimize interruptions.
- Use VBR for recording or streaming scenarios where quality is more critical than a stable bitrate.
By supporting both modes, the codec provides flexibility to meet diverse requirements for video quality and network performance.
Framerate: Encoding Up to 30FPS
How can we measure the actual frames per second?
To test the real frames per second (FPS) of an RTSP stream using PotPlayer, you can use the built-in video playback statistics feature in the software. PotPlayer provides an option to display video playback information, including the current frames per second (FPS) rate. Here's how you can test the real FPS of an RTSP stream with PotPlayer:
- Install PotPlayer: If you haven't already done so, download and install PotPlayer on your computer. PotPlayer is a multimedia player that supports various streaming protocols, including RTSP.
- Open PotPlayer and Play the RTSP Stream: Launch PotPlayer and select the option to open a network stream or URL. Enter the RTSP stream's URL or network location to start playing the stream in PotPlayer.
- Display Video Playback Statistics: While the RTSP stream is playing, right-click on the PotPlayer window to access the context menu. From the context menu, select "Playback Information" or "Statistics" (the specific label may vary based on the PotPlayer version).
- View Frames Per Second (FPS): The video playback statistics window will display information about the video being played, including the real-time frames per second (FPS) rate. Monitor the FPS value to observe the actual frame rate of the RTSP stream.
By following these steps, you can use PotPlayer to test the real frames per second (FPS) of an RTSP stream. PotPlayer's video playback statistics feature allows you to monitor the real-time FPS rate, providing insight into the smoothness and performance of the video stream playback.
Gop(Key Interval):
Why should we lower Key Interval(GOP)?
Lowering the Key interval (GOP) can help improve image quality by reducing the amount of compression applied to each frame. This can result in a higher overall image quality, especially for fast-moving or complex scenes. However, this may also increase the file size and processing requirements, so it's important to balance the trade-offs based on the specific needs of the project.
Can we set GOP(Key Interval) to 0–1 to achieve lower latency?
No, it is not possible to set the GOP (Key Interval) to 0–1 on our encoders or encoder/decoder devices. This limitation is intentional and serves to ensure the stability and reliability of the video stream. For all of our devices, the GOP is set to a minimum of 5, and the firmware does not allow adjustments below this threshold.
Why can't GOP(Key Interval) be set lower?
- Stream Stability: Allowing unrestricted GOP values could lead to stream instability, such as fluctuating video quality and unreliable transmission.
- Bitrate Management: Setting a very low GOP could result in inefficient bitrate usage, negatively affecting overall performance.
Why should we balance GOP and Framerate for optimal streaming?
It is critical to balance the GOP and frame rate settings dynamically:
- Keyframe Interval (GOP): Minimum of 5 is required to maintain efficient compression and reliable streaming.
- Frame Rate: Adjust according to application needs (e.g., 30 fps or 25 fps for real-time interaction).
Improper adjustment of these factors may lead to: Increased latency and Degraded image quality.
How to set up Frame Rate and Key Interval (GOP) for Lower Latency?
To achieve lower latency in your HDMI codec, you can configure the following parameters:
1. Frame Rate Settings
- Recommended Setting: Lower the frame rate to match the application’s requirements without compromising video quality.
- For instance, if real-time interaction is the priority, a frame rate of 30 fps or 25 fps is commonly used.
- Lowering the frame rate reduces processing and transmission delays.
2. Key Interval (GOP) Settings
- The key interval (also known as GOP – Group of Pictures) determines how often a keyframe is inserted in the video stream.
- Recommended Setting: Use a smaller key interval for lower latency, such as 1–2 seconds.
- Example: For a 30 fps video, set the key interval to 30–60 frames.
- Smaller intervals ensure that keyframes are more frequent, making it easier for the decoder to start rendering frames with minimal delay.
3. Encoder Bitrate Mode
- Choose CBR (Constant Bitrate) to stabilize the data transmission, which can help in reducing latency, especially on networks with limited bandwidth.
4. Resolution Adjustment
- Lowering the resolution (e.g., from 1080p to 720p) can also contribute to faster encoding, transmission, and decoding times.
Other Considerations:
- Ensure the network has minimal jitter and stable bandwidth to support low-latency streaming.
- If the video is being transmitted over the internet, use protocols designed for low latency, such as SRT (Secure Reliable Transport) or RTMP Low Latency.
By combining these adjustments, you can significantly reduce latency while maintaining an acceptable balance of video quality and performance.
Bitrate: 500bit/s Initially
Why do we have to set lower bitrate like 500bit/s when streaming at the very beginning?
When streaming video, setting a lower bitrate, such as 500 bits per second, at the beginning can be beneficial for a few reasons:
- Network Stability: Starting with a lower bitrate allows for a smoother start to the streaming process, especially if network conditions are variable. It ensures that the video feed can be consistently transmitted without buffer issues, even when the network might have limited bandwidth initially.
- Testing and Optimization: By starting with a lower bitrate, it provides an opportunity to test and optimize the streaming setup. It allows for assessing factors such as resolution, frame rate, and overall picture quality to find the optimal balance between video quality and bandwidth consumption.
- User Experience: A lower initial bitrate can provide a seamless start to the streaming experience for viewers. It reduces the likelihood of buffering or interruptions, which can be frustrating for the audience.
Once the streaming process is stable and optimized, the bitrate can be gradually increased to achieve higher video quality while ensuring a smooth viewing experience. This approach helps in adapting to varying network conditions and ensuring a consistent stream for viewers.
What’s the relationship between bitrate and uploading bandwidth?
The relationship between bitrate and upload bandwidth is directly proportional, as bitrate determines how much data is transmitted per second, which directly impacts the amount of upload bandwidth required.
Key Points
1. Bitrate Definition:
- Bitrate refers to the amount of data (in bits) transmitted per second during video or audio streaming. It is typically measured in kbps (kilobits per second) or Mbps (megabits per second).
2. Bandwidth Requirement:
- The upload bandwidth of your network must be higher than the bitrate for stable streaming. For instance:
- A 5 Mbps bitrate requires more than 5 Mbps of upload bandwidth to avoid buffering or stream interruptions.
3. Impact of High Bitrate:
- Setting a high bitrate consumes more upload bandwidth. If your network cannot sustain the required bandwidth, the stream may become unstable, resulting in delays, buffering, or quality drops.
4. Bandwidth vs. Bitrate:
- Bitrate is the data being transmitted, while upload bandwidth is the capacity of your network to handle this data. A mismatch can lead to performance issues.
Example Scenario
- If your ISP provides 50 Mbps upload bandwidth, you should allocate a portion (e.g., 10–15 Mbps) for video streaming and leave room for other activities like audio, metadata, or background applications.
Practical Recommendations
- Test Your Network: Measure upload bandwidth with tools like Speedtest before streaming.
- Start with Lower Bitrate: Gradually increase it based on your network’s capacity.
- Optimize Quality: Adjust video resolution, framerate, and compression to balance bitrate with bandwidth availability.
By ensuring your bitrate is compatible with your available upload bandwidth, you can achieve stable, high-quality streaming.