You can of course use Logic, Sonar, Reason, Cubase or just about any other audio program to mix a film, just as you can use iMovie and various other consumer software to edit a film. The difficulties arise when you start working at the professional level; either the tools or functions you need don't exist or to get what you need requires a time consuming work-around.
When it comes to picture editing, the workflow at the professional level is not vastly different to the workflow at the lo/no budget indie film level but this is not the case with audio post! Even low budget TV usually requires at least 2 audio post professionals (with 2 ProTools systems) and at the other extreme (high budget features) there maybe as many as 70 audio post professionals involved and as many as 50 different ProTools systems being used concurrently. How data can be moved between systems, integrated into bigger systems, replaced quickly and edited en-masse becomes of vital importance. Also, the often complex and convoluted delivery specifications for various distributors and broadcasters means the software needs to provide for complex routing schemes and all of the above needs to happen usually within unrealistic time frames, which is where the automation options and audio post centred functionality become essential.
ProTools dominates the market not because it was there first but because it has the functionality required at the professional level to get the job done in the time allowed, Logic and the other softwares mentioned do not! Not to mention that as the market leader all the specialist 3rd party audio post tools are developed primarily with ProTools in mind. The only other software which comes close and provides any realistic competition to ProTools is Nuendo.
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