H.264, 720p Video Bitrate

Question

Disclaimer: I know very little about Video codecs & encoding.

I'm developing an iOS and Android app that allows users to record videos. I want to be able to upload the videos to YouTube & have them play at 720p quality.

The videos I'm recording will always be less than 180 seconds, always be ~30fps and will always have audio.

As far as I can tell, this means I need to record at a resolution of 1280x720, then I should be good. Is this correct?
I'm trying to determine how large, on average, an H.264 video file will be per second of video. From my understanding, I need to know the bitrate of the videos. What will the bitrate of recorded H.264 video be on Android 2.2+, and iOS 5+? This Android developer page mentions a bitrate of "2Mbps" for "HD" video - is that 2 Megabytes per second or 2 Megabits per second? Will that rate be the same for any recorded H.264 video?

Part of the reason I'm so confused about this is because I did a test with 4 different Android-encoded videos of different lengths, and produced the following output;

File Size vs Time for Android-encoded H.264 videos

Wtf!?

Bonus points if you can link me to some iOS developer docs detailing this information - I've searched and can't find anything.

EDITS:

Possibly Related: H.264 file size for 1 hr of HD video
This wikipedia article mentions that the max bitrate for level 3.1 H.264 video (1280x720 @ 30fps) is from 14000 - 17500kbps.

Understanding how video formats work would be my first go-to.... — Richard J. Ross III, Oct 18 '12 at 02:40
I'm trying to, believe me, but it seems to be an incredibly complex topic. — aaronsnoswell, Oct 18 '12 at 02:44
I feel you. I have been working with video specs for more than 10 years, still never been comfortable with it. — Lazy Ninja, Oct 18 '12 at 03:12
Note that YouTube does the right thing for you, so you should just provide the best quality. The rest is pretty much out of your control anyway. — Alexis Wilke, Aug 04 '21 at 18:39

score 2 · Accepted Answer · answered Oct 18 '12 at 03:06

2

Yeah, 720p stands for 1280x720. I think it is correct.
To define how large your video file will be, you should record at a constant bitrate(CBR), but I doubt the camera will be using CBR while VBR(variable bitrate) is more efficient.
Mbps stands for Megabits per second.
I doubt that the rate will be the same as I stated earlier VBR could be used.

Edit:
Judging from the graph, it is definitely a VBR.

answered Oct 18 '12 at 03:06

Lazy Ninja

22,342
9
83
103

The outlier in the graph turned out to be recorded at a completely different bitrate / quality. I've since been scared to hell and back by the **insanely**, can't-believe-my-eyes terrible support for video recording in the Android SDK - net result, I gave up on that project. Thanks regardless! – aaronsnoswell Jan 12 '13 at 06:15

H.264, 720p Video Bitrate

1 Answers1