@rraud I agree, upload with what YT recommends.

AI Overview

YouTube recommends a 

pixel aspect ratio (PAR) of 1.000 (square pixels) for the best results. The 1.3333 pixel aspect ratio (which corresponds to a 4:3 display aspect ratio) is an older format from the days of analog video and non-widescreen TVs. 

Here is a breakdown of YouTube's recommendations for modern content:

Pixel Aspect Ratio (PAR): Always use 1.000 (square pixels). This ensures your video is not stretched or distorted on modern screens.

Display Aspect Ratio (DAR): The recommended aspect ratio is 16:9 (widescreen).

For this ratio, you should use resolutions like 1920x1080 (1080p Full HD), 1280x720 (720p HD), or higher resolutions like 4K (3840x2160).

YouTube Shorts: For vertical videos and Shorts, the recommended aspect ratio is 9:16 (e.g., 1080x1920 resolution). 

Using a 1.3333 PAR with modern codecs or platforms can lead to black bars or unwanted scaling because it's not the native format for current devices and the YouTube player. For best performance and viewer experience, stick to the modern, square pixel standards. More information is available on the official YouTube Help pages. 

 

@rraud Best you simply encode to Youtube specifications.... Which is 1920x1080 (Full HD).

I have project destined for YouTube. The source files are 1440x1080 (25fps). Is it best to render at the source file's frame size, 1440x1080 @ 1.333, or.. 1920x1080 @ 1.000.) I will probably use the Magix AVC or HVEC codec. Magix AV1 renders the video to 1920 okay but the picture is vertically elongated when rendered to 1440x1080  (@ 1.333 or 1.000).
Thanks.. my area of expertise is audio.

Sounds like HDV source files which are actually 1440x1080i50 with a PAR of 1.333 to achieve a 16:9 AR. Besides that YT expects a PAR of 1.0 as already mentioned, YT also expects progressive fields. So deinterlacing of the 1440x1080i50 source is strongly recommended. To preserve the cadans of i50 I would deinterlace to p50 instead of p25. To get best results for YT render your project to 1920x1080p50.

Thanks, The source files are16:9 wide screen.
A test render at 1440x1080 (1.3333 pixel aspect ratio) looks good as does a 1920x1080 (1.0000) rendered version. FYI, the multi-track audio (40+ tracks) were recorded to a separate audio recorder. The camera(s) audio was only used to augment the room mic tracks for applause and such. It was a funk-jazz concert with ten top-notch players. Two of the five horn players were formally with James Brown.

MediaInfo:
ID                          : 255 (0xFF)
Complete name               : C:\Users\Rick\Videos\ABB\Video files\Cam 1 (MPEG)\250515K7T2AmrodB 01 DUP.mpeg
Format                      : MPEG-TS
Commercial name      : HDV 1080i
File size                   : 8.87 GiB
Duration                    : 48 min 36 s
Start time                  : UTC 2025-05-15 21:01:27
End time                    : UTC 2025-05-15 21:51:26
Overall bit rate mode       : Variable
Overall bit rate            : 26.1 Mb/s
Maximum Overall bit rate    : 33.0 Mb/s
Encoded date                : UTC 2025-05-15 21:01:27
FileExtension_Invalid       : ts m2t m2s m4t m4s tmf ts tp trp ty

Video
ID                          : 2064 (0x810)
Menu ID                     : 100 (0x64)
Format                      : MPEG Video
Commercial name             : HDV 1080i
Format version              : Version 2
Format profile              : Main@High 1440
Format settings             : CustomMatrix / BVOP
Format settings, BVOP       : Yes
Format settings, Matrix     : Custom
Format settings, GOP        : M=3, N=12
Format settings, picture st : Frame
Codec ID                    : 2
Duration                    : 48 min 36 s
Bit rate mode               : Constant
Bit rate                    : 24.5 Mb/s
Maximum bit rate            : 25.0 Mb/s
Width                       : 1 440 pixels
Height                      : 1 080 pixels
Display aspect ratio        : 16:9
Frame rate                  : 25.000 FPS
Standard                    : Component
Color space                 : YUV
Chroma subsampling          : 4:2:0
Bit depth                   : 8 bits
Scan type                   : Interlaced
Scan order                  : Top Field First
Compression mode            : Lossy
Bits/(Pixel*Frame)          : 0.629
Stream size                 : 8.30 GiB (94%)
Color primaries             : BT.709
Transfer characteristics    : BT.709
Matrix coefficients         : BT.709

Audio
ID                          : 2068 (0x814)
Menu ID                     : 100 (0x64)
Format                      : MPEG Audio
Format version              : Version 1
Format profile              : Layer 2
Codec ID                    : 3
Duration                    : 48 min 36 s
Bit rate mode               : Constant
Bit rate                    : 384 kb/s
Channel(s)                  : 2 channels
Sampling rate               : 48.0 kHz
Frame rate                  : 41.667 FPS (1152 SPF)
Compression mode            : Lossy
Stream size                 : 134 MiB (1%)

Menu
ID                          : 129 (0x81)
Menu ID                     : 100 (0x64)
List                        : 2064 (0x810) (MPEG Video) / 2068 (0x814) (MPEG Audio) / 2069 (0x815) () / 2065 (0x811) ()