My young ears with perfect hearing can’t reliably hear a difference between mp3 @256kbps+ and flac. Just because information is discarded doesn’t mean we could have heard that discarded information in the first place.
can you hear the quiet sound of your breath while running a vacuum cleaner? Nope, the psychoacoustic model used in lossy compression knows that and will discard that and other similar sounds.
Personally, I think MP3 is outdated. AAC and vorbis are much better codecs. I can tell an mp3 encoded at 128kbps from the lossless version 95% of the time, but I have a much more difficult time with AAC at 128kbps.
Multichannel compression is even more efficient than stereo. A stereo recording at 256kbps gives 128kbps to each channel, in stereo, both channels are active nearly 100% of the time, with 5.1+ channels, a lower bitrate can be used since multichannel compression allows an encoder to allocate bits more efficiently based on which channel needs more bits, a scene with dialogue only can allow the full bitrate to be allocated to the center channel for example. The LFE channel requires very little bit allocation. I’m not sure about AAC, but I know that Dolby Digital uses a sampling rate of 240hz for the LFE channel. Due to the nyquist sampling theory, a full 48000hz sampling rate is only needed for full bandwidth channels. Dolby Digital has an effective bit depth (since lossy compression doesn’t have a true bit depth due to the Fourier transformation from the timing to frequency domain of modern transform based codecs) of 20bits, at a sampling rate of 240hz with a bit depth of 20 bits, which is high enough to accommodate the full 105dB dynamic range of film. a lossless lfe channel would only require a full 4.8kbps. I have no idea how the psychoacoustic model is applied to lfe, or if it even is, but the lfe channel hardly requires any data.
The bitrate where transparency is achieved based on my own abx testing is as follows:
MP3: 256kbps
OGG/Vorbis: 192kbps
AAC: 192kbps, some recordings 160kbps.
For multichannel formats:
Dolby Digital: 448kbps-640kbps, some scenes involving applause or rain can expose artifacts at 448kbps
DTS: 1536kbps, strangely enough, dts seems less efficient than DD, with the 768 bitrate sounding worse than 448 DD
Dolby Digital+ 5.1 (nearly all streaming sources use this): 384kbps
AAC 5.1: 350kbps vbr. 7.1: 500kbps+ vbr.
If you want to rip music to flac, go for it, but in all honesty, 320kbps AAC is more then adequate for even the most demanding recordings, and I guarantee you will lose nothing in quality that you can audibly perceive, even with the best equipment and immaculate hearing.
Honestly, I wish bluray had adopted more usage of high bitrate Dolby Digital plus (1500kbps-2000kbps) vs the space wasting lossless codecs, which have a bitrate ranging from 4mbps-6mbps. The average audio track in DTS MA or Dolby TrueHD wastes anywhere from 4-6 gigabytes of space, whereas Dolby Digital plus at a very high bitrate could reduce this size to 1-2gb, allowing things like lower video compression etc, this is even more important with UHD bluray, where video file sizes are as large as 50gb for a two hour movie.
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