Nova Guideline for Multimedia (Video and Audio)
Introduction
This guideline depicts the encoding specifications that needs to be followed, while uploading a video and audio files to your Media Library.
Generally, video cloud supports both H.264 and H.263 encoding. For most part, H.264 is suggested as it provides better quality, more extensive gadget support and utilizes AAC sound. The H.263 video utilizes only MP3 sound. Kindly follow the standards below to upload your audio and video files to the Media Library for video files and audio files that you upload to Media Library.
Video file specification
Source file naming standards
The source file name for all video and assests must be URI perfect, since it should be passed as portion of an API request during the Ingestion process. We recommend that you avoid the following in source file names.
Spaces: Use my-video.mov or my_video.mov, Instead of my video.mov
Special characters: Avoid the following characters in source file names: “!”, “@”, “#”, “$”, “%”, “^”, “&”, “*”, “(“, “)”, “?”, “/”, “\”, “{“, “}”, “[“, “]”
H.264(MPEG-4 Part 10) encoding standards
| Video Codec: | |
|---|---|
| Encoding: | 2 pass H.264 |
| Keyframe: | At least every 6 seconds |
High-resolution encoding standards
We suggest that you upload H.264 source files to video cloud to achieve high-resolution video renditions. We have arrived at this conclusion based on our test results mentioned below.
Nova test scenario
We have tested H.264 files at different sizes and aspect ratios and found that H.264 2-pass encodes with 16-bit AAC audio at a sampling frequency of 44.1kHz and a bit rate of 192 kbps. All bit rates do not include the audio bit rate, just the video. Hence, we compensate for the audio and give an approximate maximum length of the video for uploading to the server-side transcoding service.
Note:
- If video is interlaced, video cloud de-interlaces it during transcoding.
- If video is not transcoded using video cloud, de-interlace the video file before uploading it.
- If video is not transcoded using video cloud, de-interlace the video file before uploading it.
| Size | Aspect Ratio | Minimum Recommended Bit Rate |
|---|---|---|
| 640×480 | 4:3 | Video with little motion can go as low as 900 kbps with generally excellent outcomes. For overall high quality regardless of the level of motion, use at least 2672 kbps. This also refers to 720x480 sources as they are intended to be 640x480 but have a different pixel aspect ratio. |
| 640×360 | 16:9 | Video bit rate can go low as 2132 kbps in practically all cases. |
| 1024×768 | 4:3 | This format is utilized essentially in screencasts or trimmed HD sources. On account of video, 4864 kbps is adequate. On account of screencasts, we don't generally require that much information, as next to no progressions from casing to outline. We can pull off the low finish of what might accomplish for 720p, which is 3136 kbps. That is quite more than we'd need, yet we prescribe a higher bit rate to allow for more frequent keyframing. Since we don't need abnormal ghosting of the mouse, it's ideal to have extremely visit keyframes put equidistant and two times every second (so every 15 casings on account of a smooth screencast). In the event that the frame rate of the screencast isn't 30 (or 29.97), the information rate can be balanced in equal. In this way, on the off chance that you have a screencast with an edge pace of 15, the information rate would be 1568 kbps. This is liberal transmission capacity for a screencast, yet it's important to dispense with ghosting and page tearing that regularly happens when moving to something like H.264. |
| 1280×720 | 16:9 | For little motion, the data rate can go as low as 6000 kbps. At the point when movement increases, even a little, the bit rate must increase a considerable amount to redress. In occurrences of low movement which means the subjects move, yet the camera/outline doesn't, assuming lighting is satisfactory or perfect, 4512 kbps is adequate. For high movement, or to make up for different variables, 5928 kbps is adequate. |
| 1920×1080 | 16:9 stretched source | Many HD cameras utilize 4:3 sensors and stretch the picture from 1440x1080 to 1920x1080 to achieve the HD quality. At long last, this frequently brings about a picture that is similarly sharp at 960x540. In view of that, we suggest you use the below bit rate for both 960x540 and 1920x1080 formats. 1920x1080 format For high motion, the required bit rate is 8024 kbps. For little motion, the required bit rate is low as about 6000 kbps, but 8024 kbps should cover most cases.That will allow for a little over a half an hour. 960x540 format Use the same 3136 kbps rate as a 720p talking head if you are not upscaling to a larger size and if the motion is not too heavy. |
Mobile application encoding standards
At present, H.264 is the best encoding standard for applications in mobile devices which support H.264’s Baseline profile. By considering the factors like network conditions and their download speed, we suggest having at least one rendition under 130 kbps for reliable playback on cellular networks to achieve reliable performance and good quality.
Aspect ratios maintenance standards
Video Cloud maintains the same aspect ratio as the source file when it transcodes your videos. If the source files contain non-square pixels, the Video Cloud will identify and correct it to produce output videos with square pixels to achieve appropriate playback on both desktops and mobile devices.
Audio file specification
Kindly follow the specifications mentioned in the table below to achieve the best audio quality. The Note section the table below describes the possibility of errors that may occur if you failed to satisfy the audio specification.
| Specification | Note | |
|---|---|---|
| Audio | Format - Advanced Audio Coding (AAC) Duration - Same duration for both audio track and video track | if the duration fails to match, the video will be ingested, and you will probably observe playback failures under certain circumstances. |
| Audio Tracks | Enable - Enable your account for Multimedia Audio Tracks. | If not enabled, multiple audio tracks are treated as alternatives and the video cloud uses the first audio track in the video file and skips the rest. |
| Audio channels | Support - One or two audio channels. | If there are more than two audio channels, they will be merged into two, but the outcome is often unsatisfying in both cases. |
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