Why would choice D have more memory usage than choice A? I thought PCM had less overhead than Vorbis. Wouldn’t the ranking for this question be a bit different than the chosen right answer that Udemy is expecting?
I thought the rankings should be: B A D C, instead of B D A C. I based this from 2:56 & ~6:00 in the video as well as the Unity Manual for Audio Clips here: https://docs.unity3d.com/Manual/class-AudioClip.html. Am I missing something here?
Rank the memory usage of the following decompression options (highest to lowest).
A. Compressed In Memory with Vorbis
B. Decompress On Load
C. Streaming
D. Compressed In Memory with PCM
PCM compression is not as efficient in reducing file size as Vorbis. Therefore a PCM compressed file would be larger than a Vorbis compressed file.
Similarly, keeping an audio clip compressed in memory with PCM would have a higher memory usage than if it were compressed in memory with Vorbis.
The increased overhead when using Vorbis is CPU wise, because it’s a much more complex format, which thus has a higher CPU overhead to decompress when played.
Hi
I’m lost also on the same question, and after hearing twice more the course and the unity manual, i arrive to the same conclusion then Dondi_Fusco.
We are talking here about MEMORY USAGE on DECOMPRESSING. On the therms of the course, i suppose we talk about CPU usage here, because the question should be on the same subject then what we study on the course.
I would really like to have further informations or correction of the quizz, as it feel like it’s being said one thing on the course, and the inverse on the quizz.
I think the issue is with how this question is vaguely phrased regarding “memory usage”. There are several variables to consider when dealing with “overhead” and decompression. These deal with WHEN the file is pre-prepared for playback and WHEN the file is requested during runtime. There is overhead when storing a file in memory BEFORE the file is requested to play at runtime and then there is considerable overhead WHILE a particular file is requested while running.
The PCM files that are larger in filkesize and are stored in memory, do not need a decompression algorithm to playback at runtime; they are just there, ready to play. The files that are stored in a compressed state, require a decompressor while playing back at runtime to “unpack” the file, even though the filesize is smaller due to the compressor, i.e., Vorbis.
I think this is where the confusion belies this question and the reasoning for my original post when asking about “memory” and overhead. To me, the Vorbis will take-up less stored memory when prepping the file, but will take a bigger hit in processing when playing back the file vs. a PCM non-compressed file.
Hi all,
do we have any answer from the mentors regarding this topic?
According to the video and the official Unity documentation, in my opinion, Vorbis/MP3 creates more memory overhead than PCM…as you all have already mentioned
The answer is in the QA for the lecture:
quote from Sam
"… decompressed uses most as it’s completely in memory and not compressed. Streaming uses the least as it’s not in memory at all. Vorbis and PCM are in memory but compressed. Of the two Vorbis is lossy and therefore higher compression.
So the order is B,D,A,C"
