Today we looked at preparing and exporting projects for deliveries. When you are tasked with completing a project for someone, every client will have their own criteria or pre-requisites you will have to abide by for when it comes time to delivering the finished product. For example Netflix requires all audio be mixed in 48khz and 24 bit depth. They also require a 5:1 mix, the stereo mix is completely optional. If you are given a project to complete and you are not given a set criteria to follow, it is a good idea to ask to make sure the customer is getting what they need.
If you are mixing in 5:1 for example, you may need to downmix your project if required by the criteria you are given. Downmixing is the process of combining all the audio channels of a surround mix into a stereo session, typically to ensure compatibility with playback systems that cannot support the original format as well as preserving the details of the stereo image when being played through these playback systems. Some examples of this are a 5.1 movie soundtrack being downmixed for playback on a laptop with stereo speakers or a multitrack music recording (with separate vocals, instruments, etc.) being downmixed into a standard stereo mix for distribution.
When it comes to folding down a mix from 5:1 to stereo, there are two commonly used methods. LORO and LTRT. LORO, meaning left only, right only is the more commonly used method. In this procedure, the side channels are brought forward towards the centre (with the level reduced by 3db) and the LFE is discarded. LTRT, meaning left total, right total is slightly more complex in its execution. This procedure works by combining the side channels to create an “S” signal which is then added to the mix -90 degrees and +90 degrees out of phase to the left and right channels respectively.
Both methods have advantages and disadvantages. If a sound is mixed to a side channel encoded in LTRT, when decoded it will still be there. However, if played back undecoded that sound may be inaudible because of the phase alignment with the L and R channels. This is not an issue with LORO encoding, the phase is unaffected with the creation of a new mix with the L and R channels at lower overall levels. “creating a sense of distance without compromising the intelligibility of the program” (Media, 2023).
Each encoding format offers different approaches to stereo playback. LTRT is useful when it comes to working with a mono signal. In this format, a decoding matrix can be used to create a stereo image from a mono signal. On the contrary, the LORO format is useful because it uses two separate signals to create a more in-depth stereo image. It enables you greater flexibility when it comes to placing sounds in a stereo field.
By researching these methods and requirements, this will greatly help me downmix to stereo with ease, simplifying my delivery process and guiding me to stick to the right criteria. For my last surround sound mixing project in first year, I did not check the pre-requisites for my submission delivery, leading me to receive a lower grade than expected. This time round though, this will no longer be a problem because of the research I have done today.
Netflix | Partner Help Center. (2016). Post Production Branded Delivery Specifications. [online] Available at: https://partnerhelp.netflixstudios.com/hc/en-us/articles/7262346654995-Post-Production-Branded-Delivery-Specifications#h_01GBBMVW3XFY9FHESGX72KBJNK [Accessed 21 Jan. 2025].
Media, E. (2023). Downmixing LtRt vs LoRo. What’s the Difference? – Enhanced Media – Medium. [online] Medium. Available at: https://enhancedmedia.medium.com/downmixing-ltrt-vs-loro-whats-the-difference-d2071837e123 [Accessed 19 Jan. 2025].