Settings for AVCHD 2.0 Progressive compliant file, playback

[Selur]

Good to know.

Cu Selur

[Rokoko33]

One thing that still bothers me, the ratio between, the right settings for: --vbv-bufsize, --vbv-maxrate and encoding bitrate.




I am using:

• vbv-bufsize 27000 (to be safely away from max specified 28000)
  

• vbv-maxrate 25000 (to follow a guidance: Max Bitrate 27150 kbps (25000 video+ 448 audio+ 5% overhead = 26720 < 27150) 
  

• Encoding bitrate, using variable 2-pass, setting 25000 kbps.
  

But at the link below explained:

https://forum.doom9.org/showthread.php?p...ost1399419


"--vbv-bufsize 30000 --vbv-maxrate 15000 is not allowed (delay is greater than 1 second)



Basicly vbv-bufsize should newer been greater than vbv-maxrate, that is whole point."


Do I do anything wrong?

[Selur]

Link doesn't work.

"--vbv-bufsize 30000 --vbv-maxrate 15000 is not allowed (delay is greater than 1 second)
Basicly vbv-bufsize should newer been greater than vbv-maxrate, that is whole point."

That doesn't make any sense.
If the buffer size is below the vbv-maxrate the buffer couldn't be used whenever the max rate is actually used, I would say that the buffer size should be at least vbv-maxrate to be useful.

https://learn.akamai.com/en-us/webhelp/m...C6FAD.html even recommends:

We recommend a VBV buffer size of 1-5x video bitrate, ...

Also iirc. High10@4.2 uses "--vbv-maxrate 50000 --vbv-bufsize 187500" by default,..


Cu Selur

[Rokoko33]

I updated the link in my post.

---

Using Hybrid:
x264>Rate Control>VBV>using Medium Limit BD25/50 -x2, by default it sets Buffer Size = 30000, Max Fill rate = 40000.
It does not follow yours:
"If the buffer size is below the vbv-maxrate the buffer couldn't be used whenever the max rate is actually used"

[Selur]

You are right, those are the usual values for Blu-Rays.
I found the link

Maximum allowed buffer, buffer size is in relation with maxrate. Since STD Buffer Delay for Blu-Ray allows maximum 1 second. This mean to divide buffer with maxrate and see if result is less or equal to 1, if not, buffer is need to be reduced to lower value that meet 1 second STD. For BD media, maximum settings is allowed (30000), but if not meet STD Buffer Delay, then need to be reduced to lower value. For DVD media there is no maximum in Blu-Ray specification, but is strongly recommended that use less or equal to 15000, and again need to meet STD delay of 1 second.

source: https://forum.doom9.org/showthread.php?p=1399470
It's a think that is defined by the Blu-ray standard, without the context it seemed like you were implying a general rule.

Cu Selur

Ps.: Okay, after some thinking buffer below < max rate is okay, as long as you don't need a full second of buffering. (which I still find strange)

[Rokoko33]

I am worrying about opposite, Max rate below < buffer. Is this OK?

This is what I am trying to use:

• vbv-bufsize 27000 (to be safely away from max specified 28000)
  

• vbv-maxrate 25000 (to follow a guidance: Max Bitrate 27150 kbps (25000 video+ 448 audio+ 5% overhead = 26720 < 27150)
  

And setting encoding bitrate same as Max rate:

• Encoding bitrate, using variable 2-pass, setting 25000 kbps.
  

[Selur]

For Blu-ray compatibility it's not okay, you would need to use buffersize <= maxrate, due to the restrictions I quoted, so you would need to stick with 25000 for both, but that is for Blu-ray compatibility which isn't really what you are aiming for. (your should change the title of this thread btw.)
So my guess is that if TMPGEnc's AVCHD 2.0 validation doesn't complain you should be fine.

Cu Selur

[Rokoko33]

That information from:
https://learn.akamai.com/en-us/webhelp/m...C6FAD.html

Consider a small time period T over that desired to restrict the data throughput. We recommend a VBV buffer size of 1-5x video bitrate, and all renditions use the same VBV buffer size multiplier:

• VBV buffer duration = VBV buffer size / VBV maximum bitrate
  
• VBV data throughput = (T + VBV buffer duration) * VBV maximum bitrate
  

It is important to keep VBV data throughput well below the video maximum bitrate specification of the highest H.264 profile

Is quite confusing, misleading.


Looks like TMPGEnc is OK with Max rate below < buffer, when difference is small.

As per their online specs:
MPEG File for AVCHD Progressive Devices:
• Maximum Bitrate: 27150kbps (video+audio+overhead) (when the video is 1080 50/60p)
• VBV Buffer Size: Maximum 3500000 bytes (Depends on the source file Profile & Level)


From above: Max rate 27150 is below < Buffer 27343kbits (3500000 bytes).

My camcorder's 1080 60p file has VBV Buffer 3418KB (26.7Mbits), Max Bitrate 26Mbits.
It means Max rate is below < buffer (it is close but below), and it is perfectly compliant file.

All files encoded with Hybrid as Max rate is below < buffer are OK as well.
For example I encoded as Max rate 25000 is below < buffer 28000, it was all good.

I even authored BDAV structure and burnt on DVD-R disc. My BluRay players plays that disc as BDAV BluRay without issues.

Just to be on the safe side, would it be a good option to use all numbers the same: VBV Buffer = Max Fill rate = Encoder bitrate setting (General Settings>Bitrate)= 25000 ?

Also what is the correct/optimal:
x264>Frames>Weighted P-Frame Prediction>set to refs (--weightp 1) or disabled (--weightp 0) ?

[Selur]

Is quite confusing, misleading.

no it's not unless you assume that you need to be Blu-ray compatible,....

Just to be on the safe side, would it be a good option to use all numbers the same: VBV Buffer = Max Fill rate = Encoder bitrate setting (General Settings>Bitrate)= 25000 ?

I would probably go with Medium limit 'BD 25/50 - x1' (= 24 000) and also use a lower bit rate (24 000 or even lower) for the 2pass encoding.

x264>Frames>Weighted P-Frame Prediction>set to refs (--weightp 1) or disabled (--weightp 0) ?

for broader hardware support you would use --weightp 0 since some old hardware didn't support it.

Cu Selur

[Rokoko33]

I will use 25000 values since encoded file has lower values as they were set.

I was experimenting with Bitrate, Buffer size settings, found that encoded files examined by TMPGEnc shows a bit different parameters, the difference is exactly by ratio of 1.024.

For example if in Hybrid I set Buffer Size 25000kbits, an encoded file has Buffer size 3052KBytes (calculated in bits 24416kbits):
25000/24416 = 1.024

It looks like that Buffer Size values in Hybrid are actually set not as bits but as Mbits devided by 1000, not by 1024 as it should?

And the if the Bitrate values in Hybrid, for example are set to 25000kbps, an encoded file has 25.0Mbps bitrate (calculated in bits would be 25600kbps).
25600/25000 = 1.024

In TMPGEbnc if I set Bitrate values in Mbps, an encoded file has exactly (or very close) the same numerical value in MBps.

Actually the MeGUI does the same thing.
It could be x264 encoder related how it interprets input values?

Or it could be that I just misinterpret something.