If you are handling OCFs (Original Camera Files) on set for further processing or if you are involved in any post-production step, you will encounter ALE files sooner rather than later. That’s because ALEs are widely used to transfer metadata and often travel with the OCFs or the editorial clips.
The most popular use cases are probably importing and exporting ALEs with the Avid Media Composer, as Avid invented the ALE format originally. Nowadays, it is a commonly used exchange format for transferring metadata of media files between various applications. However, especially when preparing clips for the editorial department, it’s crucial to ensure that the metadata from the ALE can be linked to the related clips. Therefore it’s worth taking a closer look at how an ALE is composed and which settings affect its usability.
A bit of historical context: What is an ALE file?
In order to get a better understanding of Avid Log Exchange files, let’s take a look at their initial purpose. This is an early description from probably more than 20 years ago:
“Avid Log Exchange. A file format specifically designed to hold information about log files generated by the application. An ALE file contains information about the source material.” 
The original intention of an ALE was to help bring data from logs, such as shot logs, or telecine logs, into the Avid editing application. That way, source media captured from tape could be linked to metadata by importing an ALE into the Avid editing system. The following explanation is more up-to-date:
“An Avid Log Exchange (ALE) file is a text-based metadata exchange format used to transfer film, video, and audio data between systems. It contains important information about the media, such as Name, Filepath, Video Format, Duration, Timecode, Scene, Take, Notes, Comments, LUT information, and more.” 
This shows how the purpose of ALEs has evolved over the years: With production workflows split over many different tools and an increasing amount of information being created, a commonly accepted format to interchange became essential. Nowadays, ALEs are used to preserve and exchange shooting metadata and color grading information (such as ASC-CDL) between various editing applications for conforming, color grading, sound post-production, or to enrich the metadata of dailies distributed via dedicated streaming platforms.
Understanding the ALE file structure
ALE is a tab-limited text file composed of three sections (3). It starts with a global header section that defines general information that applies to the whole file or the project context in which it was created. It contains standard definitions (e.g., <TAB> as field delimiter) but also project-specific definitions, such as video format or FPS. They reflect the project settings from the Avid Media Composer and set global values for resolution and frame rate. Therefore it’s not possible to create ALEs for a set of clips with different frame rates. The global section is followed by a special type of table.
The keyword “Columns” marks the beginning of the standard and custom headings section. This section defines the structure for the table that is yet to come. By listing the column headers, it indicates what information is carried for each file. The headers are separated by the <TAB> character (e.g., Clip Name<TAB>In Point<TAB>Out Point).
The data headings section is the main section and contains the actual information of the clips. It is introduced with the keyword “Data”, followed by multiple rows where each row represents a clip and lists its respective metadata value in the previously defined order.
Avid already specified about 80 column headings for video and audio metadata, but you can extend the file with custom column headings. Therefore, the ALE specification does not need to be updated if any application adds new metadata fields. Any new column (header) written to the ALE file will be available as custom fields in the Avid Media Composer; for example, Silverstack recently introduced fields for ACES transforms, the ShotID, and a cue point column with timecode and marker details.
Even if many applications support reading and writing ALE files, it’s possible to create them from scratch or edit them manually if needed, e.g., to copy the values from one column into another. As ALEs are similar to CSV files, you can edit them as a spreadsheet or in a text editor. However, you need to be careful and make sure to preserve the ALE’s specific structure.
How to match ALE with Media
To enrich the media assets of your editing application or grading system with the information carried in an ALE, you need to specify which row of the ALE refers to which media asset. In order to do that link automatically, a unique identifier that is available in both the ALE and in the asset itself is required. Commonly used are combinations of the source file name, clip name, reel, or tape information. That’s why it’s crucial to consider your matching strategy when creating both the ALE and the corresponding media files to make sure the unique identifiers are available on both sides.
For Avid applications, the most convenient way is to use the tape column or, if blank, the source file column as a unique identifier because that information is also available in the header of MXF clips with DNx codec, which are natively used as Avid Media Files. The unique identifier is also essential in another context: When exporting files for conforming (online editing), the used matching criteria should also fit with the information available in the OCFs to flawlessly retrieve the right OCFs clips and conform them in a final grading timeline.
How to create ALE files
When using Silverstack, you can export pre-formatted ALEs for specific applications such as Avid Media Composer or other applications and systems like Scratch or Webgate. ALE files can be created from OCFs as well as from transcoded clips. As the most popular use case is providing data to the editing room, it’s worth taking a closer look at how that works:
As soon as the clips in Silverstack’s library are ready to be transcoded (audio files are synced, additional metadata is entered, cue points are added, etc.), you can start exporting proxy files and metadata as required by the post-production department. With Silverstack Lab, you can even create clips as MXF files (DNxHD or DNxHR) and get corresponding ALEs automatically. In the transcoding settings, you can choose the image settings like codec, resolution, or sizing, and – that’s the important part – you can also export an ALE with metadata fitting the transcoded clips.
In the ALE export wizard that can be opened from the transcoding settings in Silverstack Lab, you can choose the project’s frame rate and the metadata fields you want to include in the ALE and select the matching criteria (define the “unique identifier”). Most clips do not contain native tape information; you can choose how the information in the tape column should be generated. This selection will affect what is written to the header of the transcoded MXF files and the ALE to ensure that editorial proxies and the ALE are linkable. It depends on the source format and the post-production requirements, which metadata is relevant, and which matching criteria work best in your workflow.
Now, the MXF files can be ingested in the Media Composer and already show basic metadata derived from the file’s header information, such as timecode, name, and tape. Select those clips, choose “Input > Import Media…” from the context menu in the bin, and navigate to the ALE created before. Make sure you set the “Options” in the “Shot Log” tab to “Merge events with known master clips” before importing the ALE. That way, the metadata information from the ALE file, according to their timecode and the criteria you selected during the transfer process within Silverstack, is matched to the master clips.
You could also apply looks in the Media Composer if you also exported grading information with the ALE like ASC_SOP, ASC_SAT, or LUT. Select the clips in the bin and choose “Source Settings” from the context menu to access the “Color Encoding” options to apply CDL and LUTs to the clips.
If you are using Silverstack or Silverstack XT or just intend to use a different format than MXF with DNx, (e.g., Quicktime ProRes), the export process from Silverstack is basically the same as with Silverstack Lab, and clips can be matched by “Source File Name.” In that case, you can link or import the Quicktime files to the Avid Media Composer to merge them with the ALE.
If you only want to hand over metadata with the OCFs, you can also export fitting ALEs by selecting the OCFs in your clip library and using one of the ALE Wizards available in the Export Menu. These ALEs include metadata gathered in Silverstack, but they can also carry audio metadata. If video clips are synced with external audio files, information about the audio tracks, timecode, and sound roll is included in the ALE. That allows relinking video and audio clips later in the post process and re-using the audio-sync in another application. To learn more about transferring color metadata to the Avid Media Composer, check out this Knowledge Base article.
More tips and tricks for working with ALE files
Except for the columns that help match ALE and clips (as unique identifiers), there are some other columns worth mentioning :
- Name: This is a user-definable field to name the clip, sub-clip, sequence, etc. In Silverstack, you can choose to fill this field by using presets. If you select to leave it blank, Avid Media Composer will automatically fill the field by combining values from the scene/take columns.
- Camera: Used to identify the camera that was used to create the source (e.g., A Camera, B Camera, etc.). The camera letters can be in lower or upper case to distinguish them, for example, from camera setup letters, depending on your settings in the ALE export wizard.
- Auxiliary TC1: Silverstack fills this column with the same value as in SoundTC (AudioTC). It can be used to sync audio clips with the master clips in AVID Media Composer.
- Soundroll: ID of sound roll. A clip must contain an audio track in order for the “Soundroll” column to have a value. It’s usually not identical to the audio file name as it derives from the tape metadata of the field recorder. Sound roll values can work as matching criteria when relinking to the original audio files from ProTools.
It may happen that you lose metadata when exchanging ALEs between applications because not all of them might support the import and export of the same set of columns. That’s especially critical when it comes to relinking the source files (conforming) for final grading and sound mixing after having been passed through multiple applications. Therefore, it’s recommended to test the entire image and metadata pipeline before the shoot, which means from set to the final grading and sound mixing, especially if you set up a workflow from scratch.
And in case you lose metadata that is not critical for matching but essential for other departments (like VFX notes, lens, or camera information), it’s helpful to have your Silverstack clip library synced with ShotHub. That way, all metadata collected on set is preserved in a cloud project and retrievable by clip name or ShotID in every web browser.
That was a lot of (hopefully helpful) information, so let’s sum up a few key points: ALE files carry metadata that can be merged with clips in multiple applications. ALE files are powerful and valuable for many steps of the production process, like:
- showing an extended set of metadata for dailies streaming
- transferring metadata into editing applications (NLE)
- handing over look information from set to editing or grading systems
- preserving metadata from OCFs for the conforming process and the sound mixing
Understanding the composition of ALEs and their critical columns enables you to use them with intention and thus get the most out of them. This helps you to avoid problems in post-production.
 Avid, Avid Glossary, accessed 15 September 2022, online resource (available here).
 Steve Hullfish (2014), Avid Uncut: Workflows, Tips, and Techniques from Hollywood Pros.