Just to report a small bug that I think should be addressed.
If, for example, you're watching a 16:9 channel and then it emits a 4:3 show with the proper 4:3 signalling flag, the image will be stretched to 16:9 the only way to view it properly is to change to another channel then back again, the it will display in the proper 4:3 ratio, after that if it switches back to 16:9 you will have a squished image until you change channels back and forth again.
In summary when a channel changes aspect ratio flags, the receiver will ignore it and won't change the ratio when it should, only switching to another channel and back will make it display in the proper aspect ratio.