5 ms·

This literally addresses none of my complaints regarding Bluetooth Audio. Latency needs to be on the order of single-digit milliseconds. LC3 can achieve around

This literally addresses none of my complaints regarding Bluetooth Audio. Latency needs to be on the order of single-digit milliseconds. LC3 can achieve around 20. One order of magnitude too high. Audio needs to not sound like it's being played underwater. And give me 100 feet of range.

PaulHoule 7y ago
For the 100 feet you need more power, better antennas, and diversity reception at the headphone end. All of these could be implemented with the old Bluetooth standards but for various reasons, people haven't done it. I think with BTLE it will be easier for systems like that to operate in an infrastructure mode. That is, really my laptop should stream audio over WiFi, then it goes over Ethernet to one or more hubs near me. That's the way you get to perceived 100% reliability.
ShakataGaNai 7y ago
What is your use case for low latency? I understand that some want it for bluetooth headsets for videogames, where milliseconds mater - but beyond that? Also what about AptX LL? Or LLAC?
- lightedman 7y ago
  I play guitar. Timing is absolutely necessary. Anything past 15ms I can perceive and it is highly distracting and off-putting to my internal metronome.
  - ShakataGaNai 7y ago
    Sure. Playing music makes sense. I was just curious why people cared about 10-20ms of latency on what I see as "movie on iPad on Plane". Clearly there are many other use cases.
    - lightedman 7y ago
      "I was just curious why people cared about 10-20ms of latency on what I see as "movie on iPad on Plane"" At that latency I can see lips move before I hear audio. Very disconcerting.
- klodolph 7y ago
  If you are a musician, try introducing a 10ms or 20ms delay and then play something on piano or guitar. Whether you notice it depends on a ton of factors which I’m not going to get into, but in general, at 10ms the music will feel sluggish and you will have difficulty playing on the beat. This can be verified with ABX tests if you like. The timing accuracy for professional musicians can approach 1ms under controlled tests. The human auditory system is extremely sensitive to timing differences, among other reasons, because we use these timing differences to localize sound. 10ms is about equivalent to a 3m distance in space. So if you have a 10ms delay on your guitar, it sounds like you are playing a guitar that is 10 feet away from you.
  - unlinked_dll 7y ago
    You're not wrong, but I suggest you go out and measure the latency of pro audio wireless systems that have proprietary and specialized low-latency audio codecs. They push 10-15ms, depending on the source content. Often they trade fidelity for latency. They're also rather pricey, because it's a specialized use case. One of the tradeoffs in latency for fidelity is that the two major components of lossy codecs (the filterbank and DCT) have an inverse relationship between quality of encoding and fundamental latency built into the algorithms. The solution to your needs is a pro audio product developed by Shure or Sennheiser, not consumer electronics like bluetooth.
    - klodolph 7y ago
      The wireless systems I am thinking have published latency specs of something like 3ms, for example. It’s not worth the cost for my uses so I just stick with wires. I’m not sure which systems you are referring to that have 10ms latency, but I haven’t worked with many wireless systems so it could just be a lack of experience on my part. https://assets.sennheiser.com/global-downloads/file/12186/SK_6212_Specifications_Manufacturer_Declarations_01_2019.pdf https://assets.sennheiser.com/global-downloads/file/12186/SK... - 3ms https://www.shure.eu/productdocumentsfiles/default/products/wireless-receivers/glxd6/glxd6userguide-c44b67f219c0ede7f15233aba75dba5b.pdf https://www.shure.eu/productdocumentsfiles/default/products/... - 4ms Opus can achieve reasonable lossy compression ratios with 2.5ms packet sizes using its CELT half, which uses MDCT, so it’s definitely possible to achieve high quality under these constraints. I doubt it would make sense with Bluetooth LE because of the complexity of the codec.
ulfw 7y ago
"Audio needs to not sound like it's being played underwater." What kind of bluetooth have you been using? Modern codecs sound perfectly fine.
- monocasa 7y ago
  Modern codecs are non standard vendor extensions.
  - TylerE 7y ago
    A2DP standard supports both MP3 or AAC.
    - monocasa 7y ago
      Optionally.
      - Kirby64 7y ago
        Right, which pretty much any modern device and host supports. Any Android phone since 8.0 should have LDAC. Pretty much any headphones you would use with this should also have LDAC or AAC (or both).
  - pseudosavant 7y ago
    What do you consider a 'modern' codec? SBC is the only codec that basically can't sound good. AAC, MP3, and even ATRAC can all easily deliver 'CD Quality' sound over bluetooth, and they are all officially part of the A2DP spec. Not required codecs, but part of the spec and far from a 'non-standard vendor extension'. The only reason you need something that supports more than SBC and AAC is because of poor AAC implementations for most Android devices. AAC is very well understood, performs well, has very inexpensive FRAND licensing, and works well for every non-Android platform. And, as aptX has become incredibly common for Android, practically speaking audio sinks should only have to support AAC or aptX really. AAC for iOS/Windows/Mac/Linux and aptX for Android. Check A2DP section at https://www.bluetooth.com/specifications/assigned-numbers/Audio-Video/ https://www.bluetooth.com/specifications/assigned-numbers/Au...
Kirby64 7y ago
You're asking for a lot of pretty specialized things that don't really address the broader market. If you truly need single-digit ms latency, wired solutions or proprietary wireless is going to be better. The whole point of codecs is to use less of the incredibly congested 2.4G band and deliver similar performance. There are trade-offs, such as latency, in this case. Also, range is a component of antenna and power usage, both of which could be tailored to reach 100ft. Problem is, people would prefer smaller antennas and lower power, since 100ft of range is useless to most. There's nothing stopping Bluetooth from doing that though; it's just a matter of the devices that exist today. Not sure I can help you on the sound quality though. That sounds like a problem with the devices you've been using. AAC or LDAC both sound fine to me... and are available on pretty much any device.
TylerE 7y ago
20ms for playback of media is totally fine. (Hint: If you're standing on the opposite side of the room from a TV, you're already at about 15ms of latency...sound moves at approx. 1ft per ms) Many TVs are already delaying the audio by a frame or two anyway due to all the processing they do. It's a very very different set of requirements than real time recording/instrument playback.
- Naac 7y ago
  That seems like too much. According to this chart[0], I would say worst case scenario people are sitting 10 feet away from their television. Not to mention 15ms would imply you're 15 feet away, which I don't think is the average room size for most people. I would average worst case scenario would be 10 feet, so 10ms, and average best case would be 3 ms if you're sitting in front of your computer with speakers. [0] https://www.crutchfield.com/S-DxEcQ1ASZo9/learn/learningcenter/home/TV_placement.html https://www.crutchfield.com/S-DxEcQ1ASZo9/learn/learningcent...
  - TylerE 7y ago
    Imagine being at the bar or gym, which is the sort of use case being thrown out in this thread. 15ft is low, if anything.
- lightedman 7y ago
  "20ms for playback of media is totally fine." Not when you're wearing headphones and playing along with the music with your guitar. 20ms is more than enough to throw off even the most professional musician's timing. It's enough to throw off opera orchestral performance (and I've had it happen performing at Forrest Lawn Glen Avon near Walt Disney's tomb.) This is why I'm still using wired headphones. Latency is unacceptable in my hobbies.
  - TylerE 7y ago
    Again, performing is not playback.
audunw 7y ago
Sounds like you want a magic solution. At least if you don’t want to compromise on anything else such as distortion due to packet loss and power consumption. Bluetooth Audio is not designed for your use case. You’ll just have to deal with that.

PaulHoule 7y ago

For the 100 feet you need more power, better antennas, and diversity reception at the headphone end. All of these could be implemented with the old Bluetooth standards but for various reasons, people haven't done it. I think with BTLE it will be easier for systems like that to operate in an infrastructure mode. That is, really my laptop should stream audio over WiFi, then it goes over Ethernet to one or more hubs near me. That's the way you get to perceived 100% reliability.

ShakataGaNai 7y ago

What is your use case for low latency? I understand that some want it for bluetooth headsets for videogames, where milliseconds mater - but beyond that? Also what about AptX LL? Or LLAC?

lightedman 7y ago
I play guitar. Timing is absolutely necessary. Anything past 15ms I can perceive and it is highly distracting and off-putting to my internal metronome.
- ShakataGaNai 7y ago
  Sure. Playing music makes sense. I was just curious why people cared about 10-20ms of latency on what I see as "movie on iPad on Plane". Clearly there are many other use cases.
  - lightedman 7y ago
    "I was just curious why people cared about 10-20ms of latency on what I see as "movie on iPad on Plane"" At that latency I can see lips move before I hear audio. Very disconcerting.
klodolph 7y ago
If you are a musician, try introducing a 10ms or 20ms delay and then play something on piano or guitar. Whether you notice it depends on a ton of factors which I’m not going to get into, but in general, at 10ms the music will feel sluggish and you will have difficulty playing on the beat. This can be verified with ABX tests if you like. The timing accuracy for professional musicians can approach 1ms under controlled tests. The human auditory system is extremely sensitive to timing differences, among other reasons, because we use these timing differences to localize sound. 10ms is about equivalent to a 3m distance in space. So if you have a 10ms delay on your guitar, it sounds like you are playing a guitar that is 10 feet away from you.
- unlinked_dll 7y ago
  You're not wrong, but I suggest you go out and measure the latency of pro audio wireless systems that have proprietary and specialized low-latency audio codecs. They push 10-15ms, depending on the source content. Often they trade fidelity for latency. They're also rather pricey, because it's a specialized use case. One of the tradeoffs in latency for fidelity is that the two major components of lossy codecs (the filterbank and DCT) have an inverse relationship between quality of encoding and fundamental latency built into the algorithms. The solution to your needs is a pro audio product developed by Shure or Sennheiser, not consumer electronics like bluetooth.
  - klodolph 7y ago
    The wireless systems I am thinking have published latency specs of something like 3ms, for example. It’s not worth the cost for my uses so I just stick with wires. I’m not sure which systems you are referring to that have 10ms latency, but I haven’t worked with many wireless systems so it could just be a lack of experience on my part. https://assets.sennheiser.com/global-downloads/file/12186/SK_6212_Specifications_Manufacturer_Declarations_01_2019.pdf https://assets.sennheiser.com/global-downloads/file/12186/SK... - 3ms https://www.shure.eu/productdocumentsfiles/default/products/wireless-receivers/glxd6/glxd6userguide-c44b67f219c0ede7f15233aba75dba5b.pdf https://www.shure.eu/productdocumentsfiles/default/products/... - 4ms Opus can achieve reasonable lossy compression ratios with 2.5ms packet sizes using its CELT half, which uses MDCT, so it’s definitely possible to achieve high quality under these constraints. I doubt it would make sense with Bluetooth LE because of the complexity of the codec.

ulfw 7y ago

"Audio needs to not sound like it's being played underwater." What kind of bluetooth have you been using? Modern codecs sound perfectly fine.

monocasa 7y ago
Modern codecs are non standard vendor extensions.
- TylerE 7y ago
  A2DP standard supports both MP3 or AAC.
  - monocasa 7y ago
    Optionally.
    - Kirby64 7y ago
      Right, which pretty much any modern device and host supports. Any Android phone since 8.0 should have LDAC. Pretty much any headphones you would use with this should also have LDAC or AAC (or both).
- pseudosavant 7y ago
  What do you consider a 'modern' codec? SBC is the only codec that basically can't sound good. AAC, MP3, and even ATRAC can all easily deliver 'CD Quality' sound over bluetooth, and they are all officially part of the A2DP spec. Not required codecs, but part of the spec and far from a 'non-standard vendor extension'. The only reason you need something that supports more than SBC and AAC is because of poor AAC implementations for most Android devices. AAC is very well understood, performs well, has very inexpensive FRAND licensing, and works well for every non-Android platform. And, as aptX has become incredibly common for Android, practically speaking audio sinks should only have to support AAC or aptX really. AAC for iOS/Windows/Mac/Linux and aptX for Android. Check A2DP section at https://www.bluetooth.com/specifications/assigned-numbers/Audio-Video/ https://www.bluetooth.com/specifications/assigned-numbers/Au...

Kirby64 7y ago

You're asking for a lot of pretty specialized things that don't really address the broader market. If you truly need single-digit ms latency, wired solutions or proprietary wireless is going to be better. The whole point of codecs is to use less of the incredibly congested 2.4G band and deliver similar performance. There are trade-offs, such as latency, in this case. Also, range is a component of antenna and power usage, both of which could be tailored to reach 100ft. Problem is, people would prefer smaller antennas and lower power, since 100ft of range is useless to most. There's nothing stopping Bluetooth from doing that though; it's just a matter of the devices that exist today. Not sure I can help you on the sound quality though. That sounds like a problem with the devices you've been using. AAC or LDAC both sound fine to me... and are available on pretty much any device.

TylerE 7y ago

20ms for playback of media is totally fine. (Hint: If you're standing on the opposite side of the room from a TV, you're already at about 15ms of latency...sound moves at approx. 1ft per ms) Many TVs are already delaying the audio by a frame or two anyway due to all the processing they do. It's a very very different set of requirements than real time recording/instrument playback.

Naac 7y ago
That seems like too much. According to this chart[0], I would say worst case scenario people are sitting 10 feet away from their television. Not to mention 15ms would imply you're 15 feet away, which I don't think is the average room size for most people. I would average worst case scenario would be 10 feet, so 10ms, and average best case would be 3 ms if you're sitting in front of your computer with speakers. [0] https://www.crutchfield.com/S-DxEcQ1ASZo9/learn/learningcenter/home/TV_placement.html https://www.crutchfield.com/S-DxEcQ1ASZo9/learn/learningcent...
- TylerE 7y ago
  Imagine being at the bar or gym, which is the sort of use case being thrown out in this thread. 15ft is low, if anything.
lightedman 7y ago
"20ms for playback of media is totally fine." Not when you're wearing headphones and playing along with the music with your guitar. 20ms is more than enough to throw off even the most professional musician's timing. It's enough to throw off opera orchestral performance (and I've had it happen performing at Forrest Lawn Glen Avon near Walt Disney's tomb.) This is why I'm still using wired headphones. Latency is unacceptable in my hobbies.
- TylerE 7y ago
  Again, performing is not playback.

audunw 7y ago

Sounds like you want a magic solution. At least if you don’t want to compromise on anything else such as distortion due to packet loss and power consumption. Bluetooth Audio is not designed for your use case. You’ll just have to deal with that.