Video Upload Specification

Flow Capture will transcode just about any video or audio file you can upload into one optimized for web playback - a carefully considered balance of quality vs bandwidth requirements for streaming. When a video is uploaded to Flow Capture, multiple resolution variants are created in order to facilitate Flow Capture's Adaptive Streaming, with the highest available resolution matching that of the original file.

General SDR Upload Specifications

Our recommended file specifications for full-HD SDR video files are as follows. If you're looking for our HDR specs you can hop down now or head to our separate HDR article.

  • Resolution - 1080p or 720p
  • Codec - H.264 (also known as AVC)
  • Audio - AAC or PCM
  • Wrapper - .MOV
  • GOP - A value suitable for streaming (2-6 seconds)
  • File size - 1TB
  • Frame rate - Constant (Flow Capture does not support Variable Frame Rates at this time)

We don't recommend fast-start for H.264s as it's an older method that isn’t used in modern web players, but we will be able to process those files without issue if necessary. Flow Capture also does not support Variable Frame Rates. 

If you're uploading files in 4K SDR, there are some slight modifications to the above that you may want to take into consideration:

  • Resolution - 4K UHD (2160p)
  • Codec - H.265, ProRes LT, or H.264
  • Audio - AAC or PCM
  • Wrapper - .MOV
  • GOP - 8 or 16 seconds

We also recommend that you use a standard resolution (e.g. 4096x2160, 1920x1080, etc.) that ends in an even number, as nonstandard ones or odd numbers can result in processing failures when we're trying to encode our multiple resolutions for adaptive streaming playback. Regardless, we'll attempt to maintain whatever SDR colorspace you're working in. If it doesn't come out looking correct, please contact our support team!

Note that 4K is not enabled by default at this time, so please let us know ahead of time if you’re interested in using it!

Note that Flow Capture does not support the transcoding or playback of video files with only a single frame.

A full list of supported video formats can be found here.

Target Playback Bitrates

Folders in Flow Capture are default to the Medium bitrate. For Full HD files in SDR, that's 5000 kbps, combined audio and video. Flow Capture allows Admins to set this on a folder-by-folder basis, which can be accessed in the Asset Options of the Folder Settings tab. 

There are 4 Folder bitrate tiers:

  • Low - 3000 kbps
  • Medium - 5000 kbps
  • High - 8000 kbps
  • Very High - 10000 kbps

Bitrates Beyond SDR

The above options are for Flow Capture's default FHD SDR Folder settings. The bitrates we encode at for the playback of file types that go beyond that are as follows:

A new Folder will always default to the Medium setting, regardless of what you're uploading. You can raise that at any time by going into the Asset Options section of the Folder Settings. 

With increased bitrate comes an increased bandwidth requirement for the viewers streaming the video, meaning you will need to strike a balance when deciding which tier you set!

Dolby Vision & HDR10 Upload Specifications

If you're using Flow Capture for HDR playback, our requirements for those files are more rigorous than the ones we have for SDR video. The HDR files we generate will be HEVC 10-bit in Rec. 2020, but the colors will respect the P3 constraints within the Rec. 2020 gamut.

HDR and Dolby Vision are not enabled by default at this time, so please let us know ahead of time if you're interested in using them!

Dolby Vision

Our requirements for this format are as follows:

  • An .xml and .mov (ProRes) file pair to make each DV asset
  • Those two files will need to have the same name
  • All file names have to start with the prefix, “dovi_”
  • AAC or PCM audio
  • ProRes LT in the legal range is recommended to keep the video’s file size more manageable

We also accept higher quality ProRes files, though they will take longer to upload and process.

HDR10

The follow settings will  help you successfully upload for playback in this format.

  • Audio - AAC or PCM
  • Framerate - Less than or equal to 30fps
  • Codec - 10-bit HEVC (h265) or ProRes (min. ProRes 422) 1
  • Color Primaries - Rec. 2020, D65-P3, or SMTPE-431/SMPTE-432 (DCI-P3) 1
  • EOTF - PQ (SMPTE ST 2084) 1
  • GOP - A value suitable for streaming (2-6 seconds).
  • Color Matrix - Rec.2020 non-constant luminance 2
  • Mastering Metadata - SMPTE ST 2086 2
  • Brightness - CEA 861-3 MaxFALL and MaxCLL 2

1 Core requirements for a file to be detected for HDR processing.

2 If any of these are missing, we use the values for a Sony BVM-X300 mastering display.

If planning to conduct reviews on an iPad, you'll want to make sure to constrain any Rec. 2020 files to the that device's limit of the P3 colorspace.

When using Transkoder to create your files, you'll want to make sure that the Zero Trim setting is set to On.

DNxHD

Flow Capture supports the direct upload of DNxHD files or MOVs that have been encoded with that codec. You can send your batches of Avid OP Atom MXF files to Flow Capture through the normal upload workflow and we'll combine each of them into individual, web-playable assets (while also retaining each of the original files for download, if needed).

Here is an example of the naming convention we require:

  • File-name.mxf
  • File-name_A01.mxf
  • File-name_A02.mxf

Flow Capture can also transcode videos into DNxHD36 or 45, which is especially helpful if you're using Immediates. Another way you can take advantage of this is to use the processed dailies being uploaded to Flow Capture to generate the DNx files that might be needed by editorial.

That said, Flow Capture cannot play back the original MXF files. When you're viewing assets originated from those sources, they'll always be encoded in H.264 for playback. To take as full advantage of that quality as possible, you'll want to increase the playback bitrate in the Upload Options of the folder the files are being added to. 

It's also important to note that we cannot watermark DNx files for download, so you will need to be exercise caution when giving someone access with un-watermarked download permissions. 

Validation

Flow Capture automatically performs a pre-upload check of your video files to flag common issues and save you the time of sitting through an entire upload and processing only to find out that there was an issue wiht file names.

For a list of all the error messages, what they mean, and how to remedy them, take a look at our article on Validation Errors.