Unable to change Aspect Ration of MP4 file

Tudor

New member
I'm processing *.VRO files from a DVD recorder. They are always 4:3 and I have to use VRD to change the Aspect Ratio. When I write the output from Quickstream Fix as MP4 and do not change the Aspect Ratio upon editing and saving the file even if I specify a change of Aspect Ratio to 16:9 in the Profile it does not change it. If I write the output of the Quickstream Fix as MP4 and change the Aspect Ratio to 16:9 it is preserved as this when I edit. Does the mean you cannot change the Aspect Ratio of any MP4 file? I will try some later.
Here is the file information from the two Quickstream Fix runs:

Output of Quickstream Fix of *.VRO file with no change to Aspect Ratio:


File: Name : E:\TemporaryFiles\VideoReDo4\VR_MOVIE12.mp4
Size : 3.444 GB *******
Duration : 02:00:28.07 *******
Mux type : MP4
Video: Encoding : H.264
VideoStreamID : x201
Frame rate : 25.00 fps
Encoding size : 720 x 576
Aspect ratio : 4:3 *******
Header bit rate : 5.000 Mbps
VBV buffer : 1708 KBytes
Profile : Main/3.1
Progressive : Progressive
Chroma : 4:2:0
Entropy mode : CABAC
Bit rate : 3.660 Mbps *******
Audio Stream: 1 (Primary) Codec : AAC
Format : ADTS
Channels : 2.0
Language : eng
PID : x202
PES Stream Id : xC0
Sampling rate : 48000

Output of Quickstream Fix of *.VRO file with change to Aspect Ratio to 16*9:

File: Name : E:\TemporaryFiles\VideoReDo4\VR_MOVIE13.mp4
Size : 3.436 GB *******
Duration : 02:00:28.06 *******
Mux type : MP4
Video: Encoding : H.264
VideoStreamID : x201
Frame rate : 25.00 fps
Encoding size : 720 x 576
Aspect ratio : 16:9 *******
Header bit rate : 5.000 Mbps
VBV buffer : 1708 KBytes
Profile : Main/3.1
Progressive : Progressive
Chroma : 4:2:0
Entropy mode : CABAC
Bit rate : 3.651 Mbps *******
Audio Stream: 1 (Primary) Codec : AAC
Format : ADTS
Channels : 2.0
Language : eng
PID : x202
PES Stream Id : xC0
Sampling rate : 48000
 

Dan203

Senior Developer
Staff member
For H.264 MP4 files the aspect ratio is stored in two places. There is an aspect encoded directly into the H.264 stream called the SAR and there is an aspect encoded into the MP4 container. When you do a simple QSF we can only change the aspect of the container not the SAR value in the stream. We can only adjust the SAR value in the stream when doing a full recode. Most players will honor the aspect of the MP4 container over the SAR value, so that's usually enough, but not all will do this. And if you reopen the file in VRD it will use the SAR value because we always use the aspect from the stream and not the container. Modifying the NALs, which is where SAR and other values are stored in an H.264 stream, is a lot more difficult then modifying the header in an MPEG-2 file. It's something we would like to add in the future, but it's low priority right now.
 

Tudor

New member
Thanks very much Dan. That all makes sense, I'll just have to be careful when processing the VRO files.
 
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