1080/50p mts to Mpeg2 low Bitrates

[glenpinn]

Hi guys, i recently went on a 10 day trip interstate to shoot some video for our family archives, and i have to convert a copy of my completed 45 minute 1080/50p mp4 video to a Dvd compliant Mpeg2 program stream file, then author it to Dvd using VRD.

I had already set my usual v5 1080/50p mp4 to Mpeg2 profile up to do a forced recode, using a Min & Max bitrate of 8Mbps, which usually creates my Mpeg2 files at around 7.2 to 7.6Mbps from my source files, but something is wrong with my outputs.

Using the forced recode with the Min & Max bitrate set to 8Mbps, i end up with an Mpeg2 file @ 5.6Mbps

Using the intelligent recode my output file is only 2.8Mbps.

Any idea why this low bitrate might be happening, i thought i already sorted this issue out ages ago when testing v5.

here is my log files from both conversions (i cut a short segment from the original 45 minute source file for this test)

https://www.dropbox.com/s/wr6n3rolkodozme/VideoReDo_2014-12-01.Log?dl=0

 

[Dan203]

There is no min bitrate. Only average and max. The average should be close to the final output. The max is a value that should not be exceeded by the peak of VBR. You really shouldn't set these to be the same value, it can confuse the encoder. If you want the average to be 8Mbps then set the max to 9.5Mbps that should provide enough variance for it to work properly.

If the bitrates still end up low then it could just be that the bits aren't needed. Our MPEG-2 encoder will only use the bits it actually needs. So if the video is low motion or has a lot of black then it can lower the final bitrate. Setting the encoder quality to high in T>O>Stream params might increase it a little, at the cost of speed, but it may still end up low if the bits are just not needed.

 

[glenpinn]

Hi Dan, sorry it was a typo, i meant average and max bitrate.

Anyway, so i set the profile average to 8000 and max to 9500, output is now 7.5Mbps, so your explanation seems to support this so i wont worry about it, will leave it at 8000/9500, but why is the Intelligent Recode bitrate so low at 2.8Mbps ?

As i have previously mentioned, the so called experts in the Videohelp forum always told me to set the average and maximum bitrate to 8000 for an mpeg2 conversion, and i had always set mine to 6000 average and 8000 max, and this has always stuck in my head because i often argued this point with them and they would tell me to go away if i was not prepared to take their advice (this was when i was using TMPGE as my regular mpeg2 etiting and encoding program, and had just started using VRD) so maybe they were indeed wrong themselves.

It is ironic that i just did the same mpeg2 output using TMPGE just to test your explanation, so i set the encoding setting to Average = 8000, and in the advanced setting, the default is min = 2000 and max = 9200 so i left those alone, and the encoded file came out at 7.5Mbps so i figure that put an end to their theory, and i cannot tell any difference between the VRD output at 6.8Mbps and the TMPGE output at 7.5Mbps (both were done in progressive mode to match the source file)

 

[Dan203]

The intelligent recode has several modes, not sure which one you were using. The default is a "quality factor" mode which uses the bitrate of the original file and then adjusts it based on output codec, resolution and frame rate. The calculation is simple...

SourceQF = SourceBitate / (SourceFPS * (SourceWidth * SourceHeight) );

It's then adjusted using the codec percentages that are user settable.

Finally the output bitrate is calculated by reversing the equation...

OuputBitrate = AdjustedQF * (OutputFPS * (OutputWidth * OutputHeight) );

The other modes are target size, which calculates the bitrate based on the set size and the video length, and a static bitrate setting which uses bitrates set in the advanced dialog based on output resolution.

 

[glenpinn]

I sorted it all out now, i prefer to have the best possible quality for my Dvd conversions from my 1080/50p m2ts source files, and doing the forced recode using the average of 8000 and maximum of 9500 seems to give me around 7 to 7.5Mbps, which i am happy with, and i figured the only time i will need to drop that forced recode average and max bitrate is if i have a lengthy video that may not quite fit onto a normal 4.7gb Dvd disc, so i would lower both accordingly until the output mpeg2 will fit the Dvd after authoring.

Cheers

 

[Dan203]

Do you use VRD for authoring? If so the DVD authoring in v5 has been converted to the profile system. So there is no longer a difference between how a video is converted via Save and how it's converted when just publishing directly to DVD. So you may not need the extra step any more.

 

[glenpinn]

Do you use VRD for authoring? If so the DVD authoring in v5 has been converted to the profile system. So there is no longer a difference between how a video is converted via Save and how it's converted when just publishing directly to DVD. So you may not need the extra step any more.

yes i just figured that out last night Dan, at least VRD got their mpeg2 and authoring right, which is another reason why i love VRD.

In the past when using other Dvd authoring and burning tools, they would never do the mpeg2 conversion first and leave me a physical copy of the mpeg2 file on my hdd, then author it and burn it, all they did was convert and author directly to the Dvd folder, and i always like to have the physical mpeg2 file as well.

Later i started using TMPGE M/W 5 to convert my files to the mpeg2 interlaced video, then use the TMPGE authoring tool to output the mpeg2 file to the Dvd, now VRD does all of that for me in one go.

On another note, i have never made a habit in the past of checking my outputs to Dvd on one of my TV's as they look reasonable on my 24" screen, but man i just plugged my portable drive into my Western Digital Live media player that is connected to my 50" HD plasma TV (this has the 1366x768 resolution) and i played both the VRD Progreesive mpeg2 file and the TMPGE interlaced mpeg2 file (both were 7.5Mbps) and they both play like absolute crap.

The progressive is the better quality, it is sharper, cleaner and more vibrant, BUT it suffers from that horrible (vertical) jerkiness when the camera is panning or moving around, even the slow pans kill my eyes with that jerkiness.

The interlaced file looks all washed out, no clarity, no sharpness, and that is because this one plays with that horrible horizontal shimmering caused by the splitting of the frames.

I am now totally convinced that after watching these on TV that there is no way anyone can convert a 24Mbps 1080/50p mts file to a Dvd compliant mpeg2 file with any kind of success, unless the video has been shot in almost static mode using a tripod with next to no panning, and if that was the case, then you would definately have to convert the 1080/50p mts video in progressive mode simply because of it just looks cleaner when you look at them both frame by frame on your computer screen or on the TV.

In future, if i get a client who wants a copy of their video converted to Dvd for others to play on their old Dvd players, i think i will make sure that i change my shooting style to allow for it, just have to shoot more in a static position using my light weight fluid head tripod and do the panning as slow as i can.

 

[Dan203]

Those quality issues are more likely due to your TV. You're taking a 720x480 interlaced video and sending it to a TV with a 1366x768 progressive display. It has to both deinterlace and upsample the resolution for display. Even with the "progressive" DVD the DVD player is likely outputting as interlaced unless you have a special progressive DVD player connected via component cables so you can get true 480p.

If you watched it on a old SDTV it probably would look fine.

 

[glenpinn]

Hi Dan, yes i understand the upscaling, but the TV is still giving me exactly the same issues that i see on my 1080p computer screen with both the VRD progressive mpeg2 file and the TMPGE interlaced mpeg2 file.

The interlaced mpeg2 file shows that zigzag Jagging effect on straight horizontal or diagonal lines, but has no vertical jerkiness, but the progressive file has no horizontal zigzagging but it has that horrible vertical jerkiness in panning scenes because of the framerate drop from 50 to 25.

Also, i am not using a Dvd player, we dont use those old things in my home, we use a western digital Live hdd media player connected via HDMI, and we plug a portable usb hard drive into it to play the videos, authoring the mpeg2 files to Dvd is just for those clients who have relatives or friends who still have a Dvd player and it is the only way they can watch the videos.

To me it is just too much hassle converting these beautiful 1080/50p mp4 and m2ts files to Dvd, it is never going to work properly, and the sooner people move on from DVD format the better.