I edited a 4k project that runs about 20 minutes. I tried using the Magix codec. When I play it back it loses synch with audio over time. Source material is 3840 by 2160.
"I tried using the Magix codec."
Have you tried customizing the Mainconcept AVC render template to meet your requirements?
Or you could use an external encoder such as Handbrake either with a lossless or near lossless intermediate or using the Vegas2Handbrake setup.
I just tried modifying the MainConcept codec and it won't render to that frame size. I will try the Handbrake approach.
I was able to render UHD with a modified Mainconcept AVC Internet HD render template on Vegas Pro 13-453 without incident.
Complete name : C:\Users\John\Desktop\Render.mp4
Format : MPEG-4
Format profile : Base Media / Version 2
Codec ID : mp42 (mp42/isom)
File size : 27.0 MiB
Duration : 9 s 543 ms
Overall bit rate mode : Variable
Overall bit rate : 23.7 Mb/s
Encoded date : UTC 2017-02-13 20:07:17
Tagged date : UTC 2017-02-13 20:07:17
Video
ID : 2
Format : AVC
Format/Info : Advanced Video Codec
Format profile : High@L5.1
Format settings, CABAC : Yes
Format settings, ReFrames : 3 frames
Format settings, GOP : M=4, N=15
Codec ID : avc1
Codec ID/Info : Advanced Video Coding
Duration : 9 s 543 ms
Bit rate mode : Variable
Bit rate : 23.5 Mb/s
Maximum bit rate : 24.0 Mb/s
Width : 3 840 pixels
Height : 2 160 pixels
Display aspect ratio : 16:9
Frame rate mode : Constant
Frame rate : 29.970 (30000/1001) FPS
Standard : NTSC
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.095
Stream size : 26.7 MiB (99%)
Language : English
Encoded date : UTC 2017-02-13 20:07:17
Tagged date : UTC 2017-02-13 20:07:17
Color range : Limited
Color primaries : BT.709
Transfer characteristics : BT.709
Matrix coefficients : BT.709
Audio
ID : 1
Format : AAC
Format/Info : Advanced Audio Codec
Format profile : LC
Codec ID : 40
Duration : 9 s 515 ms
Bit rate mode : Constant
Bit rate : 192 kb/s
Channel(s) : channel0
Channel(s)_Original : 2 channels
Channel positions : Front: L R
Sampling rate : 48.0 kHz
Frame rate : 46.875 FPS (1024 spf)
Compression mode : Lossy
Stream size : 223 KiB (1%)
Language : English
Encoded date : UTC 2017-02-13 20:07:17
Tagged date : UTC 2017-02-13 20:07:17
I just tried modifying the MainConcept codec and it won't render to that frame size. I will try the Handbrake approach.
From MC section of this FAQ.
* Extreme combinations of high resolution & frame rate cause either "invalid argument" or low-memory failures but I was able to render 1920x1080@172fps and 4096x2160@59.94fps.