8Bit Depth vs 10Bit Depth Explanation for Noobs

Turtleface · 9th January 2011, 18:06

Ok, i'm new here, i made an account about 4 months ago, but never posted or visited because of that stupid 7 day wait before you can post. But now i'm stuck on this problem.

8Bit Depth vs 10Bit Depth? Advantages? Disadvantages?

I Rip PAL DVDs, would i get any extra quality with a lower bitrate with 10bit depth?

Any help would be much appreciated.

LoRd_MuldeR · 9th January 2011, 18:16

I assume you are referring to x264, right?

Yes, you can get better compression efficiency (i.e. better quality at same bitrate) with 10-Bit, even when your source is "only" 8-Bit and the final output is 8-Bit too, simply because the encoder's and decoder's internal precision is higher (-> less rounding errors). On the other hand support for 10-Bit or even 12-Bit H.264 doesn't exist in any (consumer) playback device at the moment. Even software decoders are still very rare currently. So this is something you probably don't want to use yet. Also high-bitdepth H.264 will be significant slower to encode/decode. It was said that 8-Bit basically is a trade-off for speed.

See also:
http://forum.doom9.org/showthread.php?t=155510

Blue_MiSfit · 10th January 2011, 04:51

Hi Turtleface, welcome to doom9!

Yes.

At this point, the main limiting factor in using 10 bit h.264 is the lack of a free software decoder. Mainconcept sells a payware decoder, but it's $230 last I checked. http://www.mainconcept.com/products/...broadcast.html

x264 can certainly encode 10 bit video now, even as Lord_Mulder describes, even from an 8 bit source (and there are benefits in doing so). Even though much assembly optimization has been done for 10 bit encoding, I'd assume the code isn't quite as tight as the 8 bit path, so there will likely be a noticeable speed cost.

Still, nothing wrong with doing some experimenting. Just don't expect 10 bit encodes to actually play anywhere

Derek

ajrobb · 13th January 2011, 14:46

DVDs are encoded as 11-bit DCT coefficients but I am dubious about the IDCT truncating back to 8 bits for playback.

aegisofrime · 13th January 2011, 17:15

I tried 10-bit encoding once. Speed wasn't as bad as I first thought it would be, however since there wasn't a decoder it was a really pointless exercise :/

Episodio1 · 13th January 2011, 19:05

Why only 8bit/10bit if a CPU register is 16/32/64 bits?

Where can I see this process explained to understand a bit more?

Thanks.

Dark Shikari · 13th January 2011, 19:10

Quote:

Originally Posted by Episodio1

Why only 8bit/10bit if a CPU register is 16/32/64 bits?

Where can I see this process explained to understand a bit more?

Thanks.

It is better if intermediate data values can fit in 16 bits where possible. At 11 bit, motion compensation can no longer be done in 16-bit.

Mug Funky · 14th January 2011, 04:47

@ajrobb: really? i thought DC precision was a maximum of 10-bit for DVD (and MPEG-2 goes up to 11 IIRC).

but this has no bearing on the encoding precision with respect to the output which always decodes to 8-bit

mpucoder · 14th January 2011, 05:45

DC coefficients can be 8, 9, 10, or 11 bits unsigned. AC coefficients are always 12 bits signed. I am not aware of any restriction for DVD. However, these are the encoded values, not the precision of the data they represent, which is 9 bits in MPEG-2 (not a typo, see 13818-2 Annex A).

Turtleface · 14th January 2011, 23:28

Thanks for the replies, mediacoder now supports 10 bit depth x264 encoding for those who want to know

LoRd_MuldeR · 14th January 2011, 23:52

Quote:

Originally Posted by Turtleface

Thanks for the replies, mediacoder now supports 10 bit depth x264 encoding for those who want to know

Probably because it uses x264 to do so

shae · 9th June 2015, 19:39

Actually, what does "bitdepth" mean in the context of DCT, isn't it practically an arbitrary resolution function? And how does it relate to the input/output bitdepth?

foxyshadis · 9th June 2015, 22:45

It's arbitrary, but well defined in AVC and HEVC specs. They specify the precision of the DCT output as being equal to the sample bit depth, creating scaled integer transforms with rounding and intermediate precision specified at every step, so that there's only one possible output for every input.

It's certainly possible to have, say, 16-bit DCT coefficients for all input/ouput depths, but the specs don't go that route to conserve limited hardware resources.

pandy · 12th June 2015, 12:05

Quote:

Originally Posted by mpucoder

DC coefficients can be 8, 9, 10, or 11 bits unsigned. AC coefficients are always 12 bits signed. I am not aware of any restriction for DVD. However, these are the encoded values, not the precision of the data they represent, which is 9 bits in MPEG-2 (not a typo, see 13818-2 Annex A).

AFAIR 8,9 and 10 bit DCT precision is allowed by DVD, side to this up to 10 bit data (usually in format 8.2) can be feed to encoder - usually... never saw 11 bit DCT precision in consumer market.

Quote:

Originally Posted by shae

Actually, what does "bitdepth" mean in the context of DCT, isn't it practically an arbitrary resolution function? And how does it related to the input/output bitdepth?

DCT use numeric particular precision for digital representation, video bit depth is quantization resolution (link is simple - more precise numeric DCT representation lead to lower rounding errors).

StainlessS · 13th June 2015, 06:06

HCEnc

pandy · 15th June 2015, 10:38

Quote:

Originally Posted by StainlessS

HCEnc

Not in consumer (DVD etc) profiles... - im fully aware that HCEnc offer 11 bits for DCT.

StainlessS · 15th June 2015, 13:19

Quote:

AFAIR 8,9 and 10 bit DCT precision is allowed by DVD

OK Sorry Pandy, twas above I was questioning.

shae · 11th July 2015, 12:29

How does a change in DCT resolution affect the final pixels? For example, will a 10-bit YUV input encoded with 8-bit DCT precision yield roughly the same as if the input YUV was truncated to 8-bit, or is the relation non-linear?

Quote:

Originally Posted by foxyshadis

They specify the precision of the DCT output as being equal to the sample bit depth

Sample bit-depth, as in, the source RGB/YUV?

pandy · 13th July 2015, 09:34

Quote:

Originally Posted by shae

How does a change in DCT resolution affect the final pixels? For example, will a 10-bit YUV input encoded with 8-bit DCT precision yield roughly the same as if the input YUV was truncated to 8-bit, or is the relation non-linear?

Sample bit-depth, as in, the source RGB/YUV?

There is no strict dependency except well agreed that DCT should be calculated (DCT precision) with at least 3 - 4 more bits.
Remember that DCT is different domain (frequency) and DCT describe different aspect of signal (imagine DCT as special case of FFT where whole spectrum is divided for equally spaced parts (bins) and you measuring level of frequency content in middle of the bin).

shae · 13th July 2015, 10:45

If the DCT is 11-12 bit, where are these 8 and 10 bit the thread is about?

Is there some software that can be used to quickly switch and compare different DCT resolutions on still images?

9th January 2011, 18:06	#1 \| Link
Turtleface Registered User Join Date: Oct 2010 Posts: 2	8Bit Depth vs 10Bit Depth Explanation for Noobs Ok, i'm new here, i made an account about 4 months ago, but never posted or visited because of that stupid 7 day wait before you can post. But now i'm stuck on this problem. 8Bit Depth vs 10Bit Depth? Advantages? Disadvantages? I Rip PAL DVDs, would i get any extra quality with a lower bitrate with 10bit depth? Any help would be much appreciated.

9th January 2011, 18:16	#2 \| Link
LoRd_MuldeR Software Developer Join Date: Jun 2005 Location: Last House on Slunk Street Posts: 13,223	I assume you are referring to x264, right? Yes, you can get better compression efficiency (i.e. better quality at same bitrate) with 10-Bit, even when your source is "only" 8-Bit and the final output is 8-Bit too, simply because the encoder's and decoder's internal precision is higher (-> less rounding errors). On the other hand support for 10-Bit or even 12-Bit H.264 doesn't exist in any (consumer) playback device at the moment. Even software decoders are still very rare currently. So this is something you probably don't want to use yet. Also high-bitdepth H.264 will be significant slower to encode/decode. It was said that 8-Bit basically is a trade-off for speed. See also: http://forum.doom9.org/showthread.php?t=155510 __________________ Go to https://standforukraine.com/ to find legitimate Ukrainian Charities 🇺🇦✊ Last edited by LoRd_MuldeR; 9th January 2011 at 18:26.

10th January 2011, 04:51	#3 \| Link
Blue_MiSfit Derek Prestegard IRL Join Date: Nov 2003 Location: Los Angeles Posts: 6,030	Hi Turtleface, welcome to doom9! Yes. At this point, the main limiting factor in using 10 bit h.264 is the lack of a free software decoder. Mainconcept sells a payware decoder, but it's $230 last I checked. http://www.mainconcept.com/products/...broadcast.html x264 can certainly encode 10 bit video now, even as Lord_Mulder describes, even from an 8 bit source (and there are benefits in doing so). Even though much assembly optimization has been done for 10 bit encoding, I'd assume the code isn't quite as tight as the 8 bit path, so there will likely be a noticeable speed cost. Still, nothing wrong with doing some experimenting. Just don't expect 10 bit encodes to actually play anywhere Derek __________________ These are all my personal statements, not those of my employer :)

14th January 2011, 04:47	#8 \| Link
Mug Funky interlace this! Join Date: Jun 2003 Location: i'm in ur transfers, addin noise Posts: 4,555	@ajrobb: really? i thought DC precision was a maximum of 10-bit for DVD (and MPEG-2 goes up to 11 IIRC). but this has no bearing on the encoding precision with respect to the output which always decodes to 8-bit __________________ sucking the life out of your videos since 2004

9th June 2015, 19:39	#12 \| Link
shae Registered User Join Date: Jun 2006 Posts: 409	Actually, what does "bitdepth" mean in the context of DCT, isn't it practically an arbitrary resolution function? And how does it relate to the input/output bitdepth? Last edited by shae; 11th July 2015 at 12:27.

13th January 2011, 14:46	#4 \| Link
ajrobb Registered User Join Date: Sep 2005 Posts: 2	DVDs are encoded as 11-bit DCT coefficients but I am dubious about the IDCT truncating back to 8 bits for playback.

13th January 2011, 17:15	#5 \| Link
aegisofrime Registered User Join Date: Apr 2009 Posts: 478	I tried 10-bit encoding once. Speed wasn't as bad as I first thought it would be, however since there wasn't a decoder it was a really pointless exercise :/

13th January 2011, 19:05	#6 \| Link
Episodio1 Registered User Join Date: Feb 2002 Location: Spain Posts: 198	Why only 8bit/10bit if a CPU register is 16/32/64 bits? Where can I see this process explained to understand a bit more? Thanks.

14th January 2011, 05:45	#9 \| Link
mpucoder Moderator Join Date: Oct 2001 Posts: 3,530	DC coefficients can be 8, 9, 10, or 11 bits unsigned. AC coefficients are always 12 bits signed. I am not aware of any restriction for DVD. However, these are the encoded values, not the precision of the data they represent, which is 9 bits in MPEG-2 (not a typo, see 13818-2 Annex A).

14th January 2011, 23:28	#10 \| Link
Turtleface Registered User Join Date: Oct 2010 Posts: 2	Thanks for the replies, mediacoder now supports 10 bit depth x264 encoding for those who want to know

9th June 2015, 22:45	#13 \| Link
foxyshadis Angel of Night Join Date: Nov 2004 Location: Tangled in the silks Posts: 9,549	It's arbitrary, but well defined in AVC and HEVC specs. They specify the precision of the DCT output as being equal to the sample bit depth, creating scaled integer transforms with rounding and intermediate precision specified at every step, so that there's only one possible output for every input. It's certainly possible to have, say, 16-bit DCT coefficients for all input/ouput depths, but the specs don't go that route to conserve limited hardware resources.

13th June 2015, 06:06	#15 \| Link
StainlessS HeartlessS Usurer Join Date: Dec 2009 Location: Over the rainbow Posts: 11,498	HCEnc __________________ I sometimes post sober. StainlessS@MediaFire ::: AND/OR ::: StainlessS@SendSpace "Some infinities are bigger than other infinities", but how many of them are infinitely bigger ??? Last edited by StainlessS; 16th July 2017 at 03:44.

13th July 2015, 10:45	#20 \| Link
shae Registered User Join Date: Jun 2006 Posts: 409	If the DCT is 11-12 bit, where are these 8 and 10 bit the thread is about? Is there some software that can be used to quickly switch and compare different DCT resolutions on still images?