Media Player Q&A: Q6 Is it more beneficial to handle upsampling in a media player or in a DAC?
6. Is it more beneficial to handle upsampling in a media player or in a DAC?
Jonathan Reichbach, President, Sonic Studio (Amarra)
Depending on the DAC we feel that a hardware based upsampling is superior. As computers get faster and as algorithms improve it is clear that software based upsampling (sample rate conversion) is quite possible. The best option is to manipulate the actual hardware sample rate directly and do no upsampling in software. If upsampling is required in software, we recommend it be done offline so as to not effect playback performance.Damien Plisson, Founder, Audirvana, (Audirvana Plus)
It really depends on the DAC and the quality of its internal upsampler. Often x2 oversampling using a very high quality algorithm (such as iZotope 64bit SRC included in Audirvana Plus) inside the player improves the sound quality.Tim Murison, Co-Founder & CTO, BitPerfect Sound Inc., (BitPerfect)
But I personally prefer listening to my 16/44.1 recordings using a non-oversampling multi bit DAC.
That's a complicated question. Considering only a PCM source, most DACs are sigma-delta DACs. This means they convert the PCM into a format similar to DSD before generating the analog signal. For these DACs, in my opinion, the upsampling done by the DAC is less significant to sound quality than the fact that it has converted the data. For ladder style DACs, the PCM signal is converted to analog as PCM, in these cases I think handling upsampling in the media player is preferable. The advantages being that the PC is more powerful and also might allow more choice of algorithms.Stephen F. Booth, Founder and Developer, sbooth.org, (Decibel)
In a perfect world it wouldn't matter, but in reality it can make a difference. Also, as with all things audio it depends on your setup! I think if upsampling is necessary that handling it on the software side has several advantages. The first advantage is that software upsampling can be performed using very high quality algorithms. Most, if not all DACs resample internally. Sigma-delta DACs in particular upsample to very high rates. It isn't always possible to know whether the DAC's internal filters have been carefully designed for audio quality or whether they have been designed for economy in manufacturing and power use. In the latter case, upsampling in software can be beneficial because some of the DAC's internal filtering artifacts are moved to outside the audible range. The second advantage to software upsampling is that it can be done in advance. Disk space is so cheap that it is practical to upsample all of one's music to the maximum sample rate accepted by the DAC. This eliminates any overhead caused by upsampling at the time of playback.Jussi Laako, Owner, Signalyst, (HQ Player)
In the player, since modern computers have more processing resources, and computer is something that already exists if playback software is used. It also allows constant improvements to the algorithms and completely new algorithms without replacing the hardware. Some DACs contain "DSP computers" to perform these operations, or even file playback from a memory card - these are practically blend of the two.Josef Piri & Marcin Ostapowicz, JPlay (JPlay)
I believe performing all possible operations in the playback software offers best price-performance ratio.
Software-defined radio already changed radios and made current cell-phones possible, "software-defined DACs" can change DACs drastically.
In our opinion using good upspampling algorithm on PC is superior. Also upsampling offline provides better results than upsampling online (in real-time during playback).Jim Hillegass, Founder and CEO, JRiver (JRiver Media Center)
The place it occurs is not as important as the quality of the algorithm used.Dr. Rob Robinson, Director of Engineering, Channel D, (Pure Music)
In the media player, undoubtedly.
It’s the goal of sample rate conversion to only shift the sample rate, without adding any distortion or altering (in the case of upsampling) the signal in any way.
Pure Music’s upsampling, in particular, uses a 64 bit wide pipe for the data stream and the essential reconstruction filters (which we designed from scratch in the previous century and have painstakingly optimized for fast performance and a low CPU hit on each CPU platform). Upsampling hardware typically is limited to 32 bit precision, though there are some DSP chips that use 40 or 48 bits. The highest performance is only possible with 64 bit precision. Provided the upsampling algorithm has been correctly designed and achieves the theoretical performance limit, all upsampling algorithms will then give equivalent performance, at least as far as sound quality is concerned (whether designed by Channel D or anyone else), but I think we have an edge in terms of lower CPU footprint. Then, the DAC may operate at a much higher sample rate, and artifacts of the digital to analog conversion process become less destructive to the audible frequency range.