Default vs. software vs. quick sync

billmich

Member
Having recently upgraded to an intel processor, I have been very happy at both my overall speed times, but also the ability to utilize this quick sync function. I have some questions regarding what may be minute details, but I want to make sure I understand everything down to that level of detail.

1) Most of the time, I am saving a .WTV file to MPEG2.M2TS---
a) In profile options, what is selected when the drop down is at 'default'? I'm assuming in some general settings I can select default to be either software OR quick sync?

b) In the above save scenario, what would be the biggest difference between quick sync and 1-pass software? (I fully understand 2-pass being the best quality option)

2) Some of the time, I have to save a .WTV (or an existing MPEG-2) over to H.264
a) This is where I notice Quicksync providing me the biggest time advantage over the software setting- since I am doing a full recode, are there the same differences between the QS/software as above, or are there different variables involved because it is a re-code and not an intelligent code?

3) Rarely, I will import a file from my DVR via the Colossus and those files are saved as H.264:
a) most of those times I will save again as H.264 - which setting should I use then?
b) sometimes that file is just a tiny snippet of a game and the rest of the game is in WTV (MPEG-2) - in those cases I actually want to go H.264--> MPEG-2, again, which saving mechanism do you guys suggest.

Thank you for taking the time to explain things to me.
With this information, I can go into the advanced options and make profiles for the exact scenarios that I will encounter

Thank you
 
Last edited:

Danr

Administrator
Staff member
1) Most of the time, I am saving a .WTV file to MPEG2.M2TS---
Assuming your .WTV is MPEG2, then the Default / Software / QSync has no effect. That parameter only affects things when you are doing a full recode. For intelligent processing, we always use "Software".

2) Some of the time, I have to save a .WTV (or an existing MPEG-2) over to H.264
a) This is where I notice Quicksync providing me the biggest time advantage over the software setting- since I am doing a full recode, are there the same differences between the QS/software as above, or are there different variables involved because it is a re-code and not an intelligent code?
Yes, the QS is being used because you're doing a full recode. Remember, "intelligent" can trigger a full recode too, for example converting from MPEG2 to H.264.

3) Rarely, I will import a file from my DVR via the Colossus and those files are saved as H.264:
a) most of those times I will save again as H.264 - which setting should I use then?
b) sometimes that file is just a tiny snippet of a game and the rest of the game is in WTV (MPEG-2) - in those cases I actually want to go H.264--> MPEG-2, again, which saving mechanism do you guys suggest.
For H.264 to H.264 use one of the intelligent profiles. This will be fastest and result in lowest quality change. When converting H.264 to MPEG-2, I typically use QS, for way better speed.

One thing to remember, the QS encoding is very good and very fast, but it's not as good as the software encoders, at higher quality and dual pass. The dual pass really only comes into play if you are significantly reducing the bit rate. For example, MPEG2 @ 13 Mbps to H.264 @ 6 Mbps, I would use single pass, but going to H.264 @ 2 Mbps, I would seriously consider dual pass. There are no hard and fast rules on this, easy user has to determine his own trade-offs between bit rate, quality, and encoding times.
 

billmich

Member
Dan,

Thank you for taking the time to answer. I have some further questions about your answers because I am still a learning 'noob':

#1 - answered thank you; although I guess I could have it do a 2-pass, correct? - or is that ONLY for non-intelligent (IE FULL) recodes?

#2 - what would be the trade-offs of QS vs software? QS= time shorter is one thing...

#3
a- does 'intelligent profiles' = software? you state to use "one of them" what are the options? - since it is H.264-->H.264 I am assuming you are stating it is the same as scenario #1 above, correct?
b- answered in full , QS it is

For what I am doing, I will never be reducing the bit rate that seriously in a MPEG2-->H.264 conversion; I am assuming that I can dig into the menu and change that rate. (By the way, what is the normal H.264 bit rate that the program saves at??)


from your answers it appears that I do NOTHING when it is a 'fast frame copy":
MPEG2-->MPEG 2
H.264--> H.264
WTV --> MPEG 2
(will be auto to software, no matter what)

and for the most part I would use quick sync for any full recoding:
WTV--> H.264
MPEG2-->H.264
H.264--> MPEG 2
(unless there is a massive crush down in bit rate, which for my purposes won't happen)
 
Last edited:

Danr

Administrator
Staff member
2-pass is only for full recode, and it's only enabled for software encoders. Remeber, full recode can happen with intelligent as well, such as when converting MPEG2 > H.264, etc.

The trade offs between QS and software are time vs. quality. Software will generally give you better quality, but the quality may not be noticeable if you aren't pushing the bit rates.

Intelligent will ALWAYS use software if doing a partial cut, i.e. cuts on a single GOP at the cut point. But if doing a full recode, it will use what you select.

(By the way, what is the normal H.264 bit rate that the program saves at??)
To see the saved bit rate settings, click on the Advanced Options button in the output profile. Scroll down to "Quality factor adjustment". THe default for MPEG2 > H.264 is 70%. You can change this. Personally, I think this is a bit high. I typically use 50%, which means a 10 Mbps MPEG2 gets recoded to 5 Mbps H.264.
 

billmich

Member
Thank you a bunch, this discussion has cleared up a lot of issue that I have.
70% for H.264 has worked for me to get those longer football games onto 1-disc - so I will leave it as-is.

thank you again
 

billmich

Member
now I just need to go into the advanced setting and set the 2-3 profiles I will need. I know one of the profiles will entail changing the audio to MPEG-2 and then maybe even possibly dialing it back 3.5 DB (WHEN RECORDING FROM IPAD/IpHONE..ETC)
 

billmich

Member
Intelligent will ALWAYS use software if doing a partial cut, i.e. cuts on a single GOP at the cut point. But if doing a full recode, it will use what you select.


To see the saved bit rate settings, click on the Advanced Options button in the output profile. Scroll down to "Quality factor adjustment". THe default for MPEG2 > H.264 is 70%. You can change this. Personally, I think this is a bit high. I typically use 50%, which means a 10 Mbps MPEG2 gets recoded to 5 Mbps H.264.
I saw in the advanced menu where this is set to 70. I have two questions:

1) For sports, what would be a solid bit rate I would want for H.264. I have my colussus manually set at 13 Mbps (peak at 17), I know I could definitely dial that down a tad, but I don't want to even approach bit starved status.

2) You have the MPEG--> H.264 default set at 70, if I change it to say, 50, I assume the resultant smaller file would Mux quicker and burn quicker. Would the save in VRD take longer or shorter at 50 than at 70? Would the time difference be significant or small? (I would be using quicksync)

Thank you for your responses
 
Last edited:

Danr

Administrator
Staff member
1) Don't understand the question. Isn't the Colussus already recording in H.264? The 70% would be for MPEG2 to H.264 conversion. If the original broadcast is MPEG2 @ 13 - 15 Mbps, then the Colussus should do just fine if you record at 8-10 Mbps, or even less.

2) Changing from 70% to 50% might be slightly faster since there are fewer bytes to move around. I suggest you benchmark on your system since it's impossible to predict how much improvement there might be. Be careful when benchmarking, especially if you have lots of memory (> 4GB). Unused program memory is allocated by the operating system to file cache, which means performing the same operation twice can yield very different results.
 

billmich

Member
1) Don't understand the question. Isn't the Colussus already recording in H.264? The 70% would be for MPEG2 to H.264 conversion. If the original broadcast is MPEG2 @ 13 - 15 Mbps, then the Colussus should do just fine if you record at 8-10 Mbps, or even less.

2) Changing from 70% to 50% might be slightly faster since there are fewer bytes to move around. I suggest you benchmark on your system since it's impossible to predict how much improvement there might be. Be careful when benchmarking, especially if you have lots of memory (> 4GB). Unused program memory is allocated by the operating system to file cache, which means performing the same operation twice can yield very different results.

1- My 1st question was basically ***what Mbps should I set my colossus at** I currently have it at 13Mbps, how much could I actually "dial it down" before I see goofy things/artifacts? 10Mbps? 7Mbps?..keeping in mind that I am doing this to record sports.
1A- I believe my HDHomeRun Prime is recording my events in .WTV format at about 18-19Mbps MPEG2, and that rate cannot be changed by any user setting in my devices.

2 - I have 8 GB memory. Are you saying that if I did the same thing 2 times in a row, the 2nd time would be automatically faster because of the 'cache'?

3- you mentioned before that you thought that 70 for MPEG2 --> H.264 conversions was a tad high, that's why I asked about dialing that number down as well. There also may be that rare event that runs 5-6 hours and I may need to compress lower than the 70. and if the picture is going to be undetectablly the same quality, why not speed up the whole process by crunching the file to 50? It will mux quicker and burn quicker because of its smaller size..

thank you
 

Danr

Administrator
Staff member
1. Can't say for sure, I think that question is best answered by other Colossus owners. Or you can experiment, record some sport at different bit rates. If it were me, I'd lower it to 8 Mbps.

1A. If you're recording over the air, all HD channels are required to be 19.2 Mbps, that's audio + video.

2. Yes, the 2nd time you run a benchmark it's likely going to be faster than the first.

3. I agree, I always convert my MPEG2 to H264 @ 50%. A lot depends on how picky you are as well about the output. All transcoding is lossy, just depends if it's noticeable. As an FYI, we do a lot of work for broadcasters and they typically encode their MPEG2 at 35 to 50 Mbps, and transcode it more times than you would be believe. However the high bit rate means there won't be noticable quality issues before they are ultimately transcoded down to the broadcast bit rate of 7 to 18 Mbps.
 

billmich

Member
1. Can't say for sure, I think that question is best answered by other Colossus owners. Or you can experiment, record some sport at different bit rates. If it were me, I'd lower it to 8 Mbps.

1A. If you're recording over the air, all HD channels are required to be 19.2 Mbps, that's audio + video.

2. Yes, the 2nd time you run a benchmark it's likely going to be faster than the first.

3. I agree, I always convert my MPEG2 to H264 @ 50%. A lot depends on how picky you are as well about the output. All transcoding is lossy, just depends if it's noticeable. As an FYI, we do a lot of work for broadcasters and they typically encode their MPEG2 at 35 to 50 Mbps, and transcode it more times than you would be believe. However the high bit rate means there won't be noticable quality issues before they are ultimately transcoded down to the broadcast bit rate of 7 to 18 Mbps.
Thank you so much for the great information.
1- I will set my colossus to 10 Mbps first and see how it goes, and then maybe down to 8. In this unit there is both a bit rate and a 'peak' rate that I can set, I generally set the peak rate about 2-3 Mbps higher.I think I can also set it as constant or variable. I believe I was told that variable is better..... your thoughts?

2- I am not recording any OTA, but via Comcast cable card and it seems the ESPN networks at least are in the 15-19 range, other channels have been slightly lower. I wish I could dial back the bit rate a tad there and save me from excessive editing for football games. I hit the 23.8 GB range (what will fit onto 1 BD-R) at around the 3 hour mark in MPEG-2 off of my HD HomeRun Prime;

QUESTION: What would take longer to transcode: MPEG --> H.264 at 50%, or some kind of MPEG-MPEG transcode 80-90%> (if that is even available in VRD, I thought maybe it was)

3- I will dial my rate back from 70% to 50% upon your recommendation.

QUESTION: Sometimes I have to use the joiner function to bring together games that may start on ESPNews, because the previous game runs long to my desired event.
When I am edit down each portion so that the joiner will say it is around 22.5 GB (for example). AFTER I join the segments together and open up the new file, the size will be somewhat larger, maybe 750 MB or so. Is this normal that the joined file will be larger than the sum of its component files? It is frustrating because I would love to be able to edit out commercials AND join all in one process, but because the end file is bigger than what I thought, I have to go back and re-edit more commercials out.

The combine function, in the couple of times I have tried it, will only open up the 1st file and not combine anything. I assume that it has the same restriction as join in that I cant combine a MPEG and a H.264 file together. (I will usually convert the smaller sized file over to match the larger sized file)

FINAL QUESTION: Is there any benefit (file size/time of save/compatibility) in saving in TS over M2TS?

Thank you, so much!!!
 
Last edited:

Danr

Administrator
Staff member
1. CBR vs VBR for the Colossus? No idea, but if you do hear of anything let us know.

2. Not sure. I think the MPEG2 > H264 may be faster in software. The MPEG2 > MPEG2 is faster when using QuickSync on my system (Core I7-3770), but you may get different results on your system.

3. TS vs M2TS. It's not clear, my guess is that would be similar. If the video is near constant bit rate then TS will be smaller because it has less overhead, but M2TS tends to be more compact for variable bit rates because the purpose of TS is to create a constant bit rate stream by inserting null packets. However, the default settings in VideoReDo are to omit the null packets which means it's closer to an M2TS format without the extra overhead of M2TS. This is something you can test quite easily.
 

billmich

Member
One question from above that I was wondering about and went unanswered:
I had about the joiner function making my files bigger than the sum of the respective parts...

.....and Where in the save options would I find a setting so that a 27 GB file (or whatever) can be saved at 80% (or whatever the number needs to be) so that the resulting file is under the magical 23.8GB size. I guess if at all possible, I would rather keep the file in MPEG over transcoding it to H.264 if most all else is equal

I would love to compare save times as I also have an i7 processor

Thank you
 
Last edited:

billmich

Member
you said you were transcoding mpeg2 to mpeg2.
That quote should not have been in my reply,I have removed it

Q1: Why does the joiner function make my file bigger than the sum of its parts, and by how much usually?

Q2: where do I find the advanced option of saving MPEG2--> MPEG 2 but in such a way that it will shrink my file size to match the BD-R disc capacity?
 
Last edited:

Danr

Administrator
Staff member
Q1: No idea, need more information. Usually output is within a few % of the sum of the parts.

Q2: a) Set the output mode to "Force recode". b) Then next to Avg. Bitrate is a calculator symbol. Press that to assist you in determining the bit rate to match your destination size requirements.
 

Danr

Administrator
Staff member
I realized there's another option for Q2: On the advanced tab, scroll down to Intelligent Recode Options. Change the Bitrate calulation mode to "Target File Size". This should automatically set the average bit rate and force a transcode if the file is larger than the Target size.

Personally, I don't use that option which is why I forgot about it.

Hope that helps.
 

jmc

Active member
I realized there's another option for Q2: On the advanced tab, scroll down to Intelligent Recode Options. Change the Bitrate calulation mode to "Target File Size". This should automatically set the average bit rate and force a transcode if the file is larger than the Target size.

Personally, I don't use that option which is why I forgot about it. Hope that helps.
One thought on Target File Size"...

"Dual Pass" (more time) is likely to be much more accurate hitting the target file size.
But test and find out what suits your needs best.

jmc
 
Top Bottom