Broadcasting Tips: QC’ing and Transcoding files

In media production, building QC (quality check) and transcode files for use in manual and automated workflows typically involves the following steps:

1. Determine the specifications: Identify the technical requirements for the media file based on the delivery platform or distribution channels. This includes file format, resolution, aspect ratio, bit rate, frame rate, audio format, and other technical parameters.

2. Encode or transcode: Once the file specifications are defined, use a transcoding software to encode or transcode the media file to the desired specifications. This process converts the file from its original format to the required delivery format. Ensure the output quality is up to the expected standards.

• Note: Encoding and transcoding are both processes of converting digital media files from one format to another. However, there is a distinction between these two processes that is important to understand.

Encoding refers to the process of compressing digital media files into a specific format to reduce file size while retaining as much quality as possible. This compression can be lossless or lossy, depending on the encoding method used.

Transcoding, on the other hand, involves taking an already compressed media file and re-compressing it into a different format or bitrate. This can involve changing the media file’s resolution, aspect ratio, frame rate or other technical parameters.

While both encoding and transcoding can be used to reduce file sizes, encoding typically involves compressing high-quality files for use in delivery platforms while transcoding focuses more on adapting existing media files to suit a variety of distribution and delivery platforms.

The main difference lies in the fact that encoding is the process of compressing an un-compressed file for storage or streaming purposes, while transcoding is the process of converting an already compressed file into a different format, resolution, and/or bit rate.

3. QC check: Once the file is transcoded, it must be tested to ensure it meets technical specifications and quality levels. This can be done manually or through an automated quality control system that checks for technical issues such as pixelation, color accuracy, brightness, and resolution.

To specifically test QC’d video and ensure it meets technical specifications and quality levels, you can follow these steps:

• Check the video resolution: Ensure the video resolution matches the intended output specifications. For instance, if the video is meant for a 1080p output, verify that the resolution is 1920×1080.

• Verify aspect ratio: Verify if the aspect ratio of the video is correct. This can typically be set to 16:9 or 4:3.

• Check bit rate: Verify that the video’s bit rate meets specified requirements. This will affect the video quality, and too high or too low bit rates can result in poor quality.

• Test audio quality: Check audio levels, clarity, and timing. Ensure audio levels don’t clip or distort, and that the audio is synced correctly to the video.

• Check color and exposure: Verify the color accuracy and exposure levels of the video. Ensure that the colors are not too saturated or de-saturated and that the exposure levels are not too bright or too dark.

• Run tests for technical issues: Quality control software can automate this step by running a series of automated tests to check for technical issues. Some common issues software can detect include pixelation, interlacing, dropouts, and compression errors.

Here are ten series of automated tests that are commonly used to check for technical issues in the broadcast media industry’s QC process:

– Video signal analysis: This involves analyzing the video signal to detect issues such as missing or duplicate frames, video compression artifacts, and signal dropout.

– Audio level analysis: This involves analyzing the audio levels to verify that they are within acceptable levels and that there are no audio dropouts.

– Lip sync analysis: This test checks that the audio and video are in sync with each other, with no noticeable delays or desyncs.

– Closed captioning analysis: This involves analyzing the closed caption data to ensure that they are synced correctly with the audio and video.

– Loudness compliance analysis: This test ensures that audio levels comply with relevant loudness guidelines, such as CALM Act.

– Video quality metrics: This measures various video quality metrics, such as Peak Signal-to-Noise ratio (PSNR), Structural Similarity (SSIM) and Mean Opinion Scores (MOS), to ensure that the video is of high quality.

– Aspect ratio and resolution compliance: This test ensures that the video’s aspect ratio and resolution comply with relevant specifications.

– Subtitle and caption compliance: This verifies that subtitles and captions adhere to standards and are free from errors.

– Compression analysis: This test checks that the video encoding and compression have been applied correctly, and verifies that bitrates aren’t too high or low.

– Color and gamma analysis: This test verifies correct color space and level and image brightness or dark values through gamma analysis. 

These automated tests help ensure that broadcast media content is delivered to its intended specifications, and adheres to industry standards for technical quality.

– Check for legal compliance: Verify that the video does not contain any copyright infringements or other legal compliance issues.

4. Review and revise: Once QC checks are complete, review the results and revise any errors or issues that were found. This can involve making additional cuts, color correction, or other adjustments.

5. File-naming convention and metadata: Consistent file naming convention and metadata is essential to ensure the media assets are managed and distributed optimally. Using a bespoke asset management system or media production software that tag and track the files and the corresponding metadata allows for efficient and accurate searching and retrieval for the use of the assets in future projects.

By following these steps, media producers can ensure that their assets are optimized for different platforms and workflows while also making sure that the files meet the required technical standards for delivery.