Poor Dynamic Range - Even with Full enabled

[Colonel Badger]

Hmm, I feel like most of the time when I'm watching content I see the DD5.1 or bitstream icon lit up on my receiver. Now I'm second guessing myself, going to check later when I'm home. Most of my content is being played through Plex. Maybe Plex can bitstream?

You are correct. DD.5.1 is more than likely appearing on your receiver. The problem is that Apple is decoding and then re-encoding the DD.5.1 stream and in the process losing dynamic range. Your receiver is seeing the re-encoded DD5.1 stream.

We're asking for a "passthrough" that doesn't do that.
[doublepost=1453750165][/doublepost]On another note, wonder if 9.1.1 has helped any ?

 

[profets]

You are correct. DD.5.1 is more than likely appearing on your receiver. The problem is that Apple is decoding and then re-encoding the DD.5.1 stream and in the process losing dynamic range. Your receiver is seeing the re-encoded DD5.1 stream.

We're asking for a "passthrough" that doesn't do that.
[doublepost=1453750165][/doublepost]On another note, wonder if 9.1.1 has helped any ?

Ahh, that's good to know. Thanks.

To answer the original question, I have been happy with the audio, I really do enjoy 5.1 and having a decent setup, but I'm also far from an audiophile that would notice differences in encoding.

 

[geesus]

Is it any better after the latest software update?

 

[kagharaht]

Is it any better after the latest software update?

No. Still dumb down DD.

 

[Dave84]

Having the same issues myself with ATV 4. Volume is considerably lower and the dynamic range lacks punch in the action scenes and bass areas.

Just did a quick switch out and put my ATV 3 back in place and it sounds so much better. Really frustrating as I love the UI and speed of the new ATV but the poor audio performance is a deal breaker for me. I'll condemn the ATV 4 to the bedroom and keep my old ATV 3 in the living room. Hopefully an os update can fix this and I can switch them back sooner rather than later.

 

[tjwilliams25]

Having the same issues myself with ATV 4. Volume is considerably lower and the dynamic range lacks punch in the action scenes and bass areas.

Just did a quick switch out and put my ATV 3 back in place and it sounds so much better. Really frustrating as I love the UI and speed of the new ATV but the poor audio performance is a deal breaker for me. I'll condemn the ATV 4 to the bedroom and keep my old ATV 3 in the living room. Hopefully an os update can fix this and I can switch them back sooner rather than later.

Do you notice the range get better with a volume increase? I certainly do on my setup, which I have a dedicated receiver. The only detriment I notice with surround audio from any app is that it is quieter. I can only ascertain that this is from the LPCM 7.1 stream going to my receiver from the Apple TV, as my PS3 used to do the same thing when I set it to LPCM instead of Dolby. Like I said earlier in the thread, this is because Dolby performs waveforming and loudness modulation on the stream to make it seem punchier even though it is pretty compressed. LPCM is raw, uncompressed sound data, without any added loudness effects, so your receiver is just outputting it the way it should. I agree Apple should give us a choice to be able to switch between the LPCM and Dolby streams, depending on our taste.

 

[Dave84]

Do you notice the range get better with a volume increase? I certainly do on my setup, which I have a dedicated receiver. The only detriment I notice with surround audio from any app is that it is quieter. I can only ascertain that this is from the LPCM 7.1 stream going to my receiver from the Apple TV, as my PS3 used to do the same thing when I set it to LPCM instead of Dolby. Like I said earlier in the thread, this is because Dolby performs waveforming and loudness modulation on the stream to make it seem punchier even though it is pretty compressed. LPCM is raw, uncompressed sound data, without any added loudness effects, so your receiver is just outputting it the way it should. I agree Apple should give us a choice to be able to switch between the LPCM and Dolby streams, depending on our taste.

I only get DD when I set the ATV to do so. If I leave it on auto I only get 2.0 stereo through my receiver. This applies to both iTunes purchases and my personal ripped blurays.

With the ATV I could set the audio to auto and it would select the DD track and play at full (normal) volume with full dynamic range.

 

[geesus]

I wonder if disabling menu sound effects would have any impact. If the soundtrack is having to add those as well, it must dilute it somehow.

 

[Colonel Badger]

Do you notice the range get better with a volume increase? I certainly do on my setup, which I have a dedicated receiver. The only detriment I notice with surround audio from any app is that it is quieter. I can only ascertain that this is from the LPCM 7.1 stream going to my receiver from the Apple TV, as my PS3 used to do the same thing when I set it to LPCM instead of Dolby. Like I said earlier in the thread, this is because Dolby performs waveforming and loudness modulation on the stream to make it seem punchier even though it is pretty compressed. LPCM is raw, uncompressed sound data, without any added loudness effects, so your receiver is just outputting it the way it should. I agree Apple should give us a choice to be able to switch between the LPCM and Dolby streams, depending on our taste.

I'm not sure I agree with this. For one the stream is encoded as Dolby and then is decoded before transmitting as PCM to your receiver, based on your theory haven't you already lost detail (compression). Also I have plenty of other sources using Dolby that are much more dynamic/punchy. I would also add that the Infuse App playing Dolby DD 5.1 from the ATV from DVD MKV files sounds MUCH more dynamic that the iTunes movies. It's not a Dolby vs PCM thing per se, it's something else Apple is doing that loses Dynamic Range.
[doublepost=1453922557][/doublepost]

I wonder if disabling menu sound effects would have any impact. If the soundtrack is having to add those as well, it must dilute it somehow.

Hmmm that's an interesting thought!

 

[Dave84]

I'm not sure I agree with this. For one the stream is encoded as Dolby and then is decoded before transmitting as PCM to your receiver, based on your theory haven't you already lost detail (compression). Also I have plenty of other sources using Dolby that are much more dynamic/punchy. I would also add that the Infuse App playing Dolby DD 5.1 from the ATV from DVD MKV files sounds MUCH more dynamic that the iTunes movies. It's not a Dolby vs PCM thing per se, it's something else Apple is doing that loses Dynamic Range.
[doublepost=1453922557][/doublepost]

Hmmm that's an interesting thought!

I'm no audio expert but I think I'm right in saying the ATV 3 just passed through the signal without doing anything to it. It appears the ATV is doing some processing witchcraft to the source and messing with the dynamic range.

I've tried with the sound effects on and off and it makes no difference.

 

[Colonel Badger]

I'm no audio expert but I think I'm right in saying the ATV 3 just passed through the signal without doing anything to it. It appears the ATV is doing some processing witchcraft to the source and messing with the dynamic range.

I've tried with the sound effects on and off and it makes no difference.

I believe ATV 3 took the bitstream out of the source and sent it to the receiver unchanged. ATV 4 is decoding the bitstream futzing with it and then re-encoding it for DD 5.1 delivery, or sending it as PCM.

 

[tjwilliams25]

I'm not sure I agree with this. For one the stream is encoded as Dolby and then is decoded before transmitting as PCM to your receiver, based on your theory haven't you already lost detail (compression). Also I have plenty of other sources using Dolby that are much more dynamic/punchy. I would also add that the Infuse App playing Dolby DD 5.1 from the ATV from DVD MKV files sounds MUCH more dynamic that the iTunes movies. It's not a Dolby vs PCM thing per se, it's something else Apple is doing that loses Dynamic Range.
[doublepost=1453922557][/doublepost]

Hmmm that's an interesting thought!

I'm not arguing that the Apple TV isn't doing something along the way, I was just trying to say that with my current setup, I'm not noticing the dynamic range issues that everyone else seems to be having an issue with. And that's with using a bunch of different apps and videos. The only thing that is consistent is the fact that I have to turn my receiver up 15 units more. It would be easier to discern what the problem was if both Apple TVs output in the same format, but as they don't it feels kind of like we're just spinning our tires.

 

[Rigby]

Do you notice the range get better with a volume increase? I certainly do on my setup, which I have a dedicated receiver. The only detriment I notice with surround audio from any app is that it is quieter. I can only ascertain that this is from the LPCM 7.1 stream going to my receiver from the Apple TV, as my PS3 used to do the same thing when I set it to LPCM instead of Dolby. Like I said earlier in the thread, this is because Dolby performs waveforming and loudness modulation on the stream to make it seem punchier even though it is pretty compressed.

In fact, this is probably caused by the AC3 Dialnorm feature. Basically, AC3 streams can contain metadata that tells the output device (e.g. an AV receiver) at what volume the audio should be played. The goal is to achieve a consistent level across different sources. LPCM has no such feature. Some receivers have a setting to turn Dialnorm on or off.

AC3 encoders do not do any "wave forming" (the AC3 compression algorithm does not reduce dynamic range).

 

[priitv8]

In fact, this is probably caused by the AC3 Dialnorm feature.

As a matter of fact, the new aTV 4 is the first one, whose stream also shows DIALNORM=31 on my receiver. No earlier aTV did this.

 

[Colonel Badger]

In fact, this is probably caused by the AC3 Dialnorm feature. Basically, AC3 streams can contain metadata that tells the output device (e.g. an AV receiver) at what volume the audio should be played. The goal is to achieve a consistent level across different sources. LPCM has no such feature. Some receivers have a setting to turn Dialnorm on or off.

AC3 encoders do not do any "wave forming" (the AC3 compression algorithm does not reduce dynamic range).

Since Dynamic Range Control and DialNorm are interlinked when decoding you could be right.

 

[tjwilliams25]

In fact, this is probably caused by the AC3 Dialnorm feature. Basically, AC3 streams can contain metadata that tells the output device (e.g. an AV receiver) at what volume the audio should be played. The goal is to achieve a consistent level across different sources. LPCM has no such feature. Some receivers have a setting to turn Dialnorm on or off.

AC3 encoders do not do any "wave forming" (the AC3 compression algorithm does not reduce dynamic range).

I agree. Thanks for correcting me, I'm not sure if I'm remembering the article that I read a while ago wrong or if I'm just silly, but that's totally what I meant.

 

[Rigby]

Since Dynamic Range Control and DialNorm are interlinked when decoding you could be right.

Not really. Dialnorm only affects the playback volume, not the dynamic range. I'm still not sure if the ATV actually reduces the dynamic range or just the volume (can be hard to tell without comparing with the level-matched original source).

 

[Colonel Badger]

Not really. Dialnorm only affects the playback volume, not the dynamic range. I'm still not sure if the ATV actually reduces the dynamic range or just the volume (can be hard to tell without comparing with the level-matched original source).

My understanding was that Dialnorm is used as a reference for dynamic range control. It's used as the center reference of what ever DRC preset included in the metadata. So if the the Dialnorm is too high or too low it will affect range.

 

[Rigby]

My understanding was that Dialnorm is used as a reference for dynamic range control. It's used as the center reference of what ever DRC preset included in the metadata. So if the the Dialnorm is too high or too low it will affect range.

Dialnorm is used as the "neutral" level *if* dynamic range compression is applied. But of course, if you want to hear full range, you will not enable dynamic range compression in your equipment, and in this case Dialnorm does not have any effect whatsoever on dynamic range (and the DRC profiles in the metadata will be ignored).

 

[Colonel Badger]

Dialnorm is used as the "neutral" level *if* dynamic range compression is applied. But of course, if you want to hear full range, you will not enable dynamic range compression in your equipment, and in this case Dialnorm does not have any effect whatsoever on dynamic range (and the DRC profiles in the metadata will be ignored).

Thanks Rigby. You are correct. I'm just trying to understand why the stream from ATV seems less punchy than the equivalent stream for the same movie say from DVD. It's possible that the Dialnorm being "low" just makes it feel less punchy and simply turning up the amp will solve this. But in my experience that doesn't seem to be the case. I turn it up and it's louder but still doesn't seem to have the "impact" or punch. A DVD (mkv's) played via Infuse on the same ATV has way more punch.

So is it possible that Apple is incorrectly/mistakenly encoding and enabling say a DRC profile of film standard when DRC is disabled, and a film light profile when DRC is enabled on the ATV. Sounds completely wrong and I would really hope not but in my experience it would answer what I'm hearing.

Alternatively they're drastically reducing bitrate when re-encoding which would also impact clarity.

They're definitely doing something and it seems at least to my ears more than just "low" Dialnorm.

 

[geesus]

I'm no expert on such matters, but surely they must be manipulating the audio in some way, to keep menu sound effects audible during films etc? That's without even mentioning Siri. If I jump between Netflix on my ATV4 and PS4 the difference in audio is like night and day - it's not just a small difference in dynamics (though admittedly the audio on the PS4 is DD+)

 

[simon lefisch]

While I don't have an ATV, I do encode videos to play on my system. I will say one thing that I've noticed, most HD movies use a DTS-HD audio track, while others use Dolby True-HD. When encoding the movie I typically use the DTS Passthru option to pass the original DTS audio. Here's the kicker, an mkv file is the only format that will hold the DTS audio (at least, I haven't been able to get it on an MP4). So when Apple is encoding the movie, they are re-encoding the DTS audio to DD, since all there movies are MP4's. I have done this in the past and noticed the audio doesn't have the dynamic range as the original audio track does. I believe this has a lot to do with the lack of dynamics found in most to all of the movies found in iTunes.

 

[bluespark]

While I don't have an ATV, I do encode videos to play on my system. I will say one thing that I've noticed, most HD movies use a DTS-HD audio track, while others use Dolby True-HD. When encoding the movie I typically use the DTS Passthru option to pass the original DTS audio. Here's the kicker, an mkv file is the only format that will hold the DTS audio (at least, I haven't been able to get it on an MP4). So when Apple is encoding the movie, they are re-encoding the DTS audio to DD, since all there movies are MP4's. I have done this in the past and noticed the audio doesn't have the dynamic range as the original audio track does. I believe this has a lot to do with the lack of dynamics found in most to all of the movies found in iTunes.

True, but to be clear we are discussing a playback problem with the ATV4 that is not limited to iTunes movies or even MP4s. Any movies, including but not limited to those, will be output differently on the ATV4 than on the ATV3 (or any other device I'm familiar with). The issue also affects music files.

 

[Colonel Badger]

While I don't have an ATV, I do encode videos to play on my system. I will say one thing that I've noticed, most HD movies use a DTS-HD audio track, while others use Dolby True-HD. When encoding the movie I typically use the DTS Passthru option to pass the original DTS audio. Here's the kicker, an mkv file is the only format that will hold the DTS audio (at least, I haven't been able to get it on an MP4). So when Apple is encoding the movie, they are re-encoding the DTS audio to DD, since all there movies are MP4's. I have done this in the past and noticed the audio doesn't have the dynamic range as the original audio track does. I believe this has a lot to do with the lack of dynamics found in most to all of the movies found in iTunes.

That wouldn't explain why the exact same movie played through an ATV 3 sounds better/more dynamic.

 

[Robdmb]

I am confused. Can someone confirm if its best to leave the audio to "Auto" (where I get PCM output) or "Surround" (where i seem to get DD output)? Thanks.