[Nexus 4 Q&A, Help & Troubleshooting] Alex240188:
Pixel Count

1280 x 720 = 921600

1920 x 1080 = 2073600

2.25 x more between 720 & 1080

your 1080 video should be at least 225% larger at 81.9MB at the same compression

your 1080 recording only has 22% higher file size at 44.5MB

Video Info Breakdown - useful info will be listed below before the full breakdown

720p

Overall bit rate : 16.9 Mbps

Frame rate : 24.922 fps

Minimum frame rate : 23.759 fps

Maximum frame rate : 26.216 fps

1080p

Overall bit rate : 20.3 Mbps

Frame rate : 30.292 fps

Minimum frame rate : 18.304 fps

Maximum frame rate : 31.813 fps

Summary

As you can see the target framerate was 24.9fps in your 720p video, which it kept to very closely <1.5fps deviation.

Whereas in your 1080p video the target was 30.3fps and in some instances it dropped as low as 18.3 fps (thats a whopping 12fps loss at some points.

there is a fine line between good compression and good picture quality.

from looking at the videos you have provided My best guess is that the nexus 4 cannot handle 1080p recording

it struggles to keep up with the fps & I would also have said that the bitrate should have been much higher than it is on a 720p recording (upon further inspection, most of my HD videos only have a bitrate of about 7.5Mbps), but my guess is that it is trying to record with a higher bitrate in 1080p and it cannot actually record at the speed it wants to resulting in slowdowns in fps while bottlnecking & also worse compression.

RAW DATA BELOW

720p

General
Complete name : V:\Downloads\720P.mp4
Format : MPEG-4
Format profile : Base Media
Codec ID : isom
File size : 36.4 MiB
Duration : 18s 90ms
Overall bit rate : 16.9 Mbps
Encoded date : UTC 2013-09-20 17:58:38
Tagged date : UTC 2013-09-20 17:58:38

Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : Baseline@L3.2
Format settings, CABAC : No
Format settings, ReFrames : 1 frame
Format settings, GOP : M=1, N=30
Codec ID : avc1
Codec ID/Info : Advanced Video Coding
Duration : 17s 776ms
Bit rate : 16.8 Mbps
Width : 1 280 pixels
Height : 720 pixels
Display aspect ratio : 16:9
Frame rate mode : Variable
Frame rate : 24.922 fps
Minimum frame rate : 23.759 fps
Maximum frame rate : 26.216 fps
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.731
Stream size : 35.6 MiB (98%)
Title : VideoHandle
Language : English
Encoded date : UTC 2013-09-20 17:58:38
Tagged date : UTC 2013-09-20 17:58:38

Audio
ID : 2
Format : AAC
Format/Info : Advanced Audio Codec
Format profile : LC
Codec ID : 40
Duration : 18s 90ms
Source duration : 18s 96ms
Bit rate mode : Constant
Bit rate : 192 Kbps
Nominal bit rate : 96.0 Kbps
Channel(s) : 1 channel
Channel positions : Front: C
Sampling rate : 48.0 KHz
Compression mode : Lossy
Stream size : 424 KiB (1%)
Source stream size : 424 KiB (1%)
Title : SoundHandle
Language : English
Encoded date : UTC 2013-09-20 17:58:38
Tagged date : UTC 2013-09-20 17:58:38
mdhd_Duration : 18090

1080p

General
Complete name : V:\Downloads\1080P.mp4
Format : MPEG-4
Format profile : Base Media
Codec ID : isom
File size : 44.5 MiB
Duration : 18s 346ms
Overall bit rate : 20.3 Mbps
Encoded date : UTC 2013-09-20 17:59:21
Tagged date : UTC 2013-09-20 17:59:21

Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : Baseline@L4.0
Format settings, CABAC : No
Format settings, ReFrames : 1 frame
Format settings, GOP : M=1, N=30
Codec ID : avc1
Codec ID/Info : Advanced Video Coding
Duration : 18s 69ms
Source duration : 18s 90ms
Bit rate : 20.3 Mbps
Width : 1 920 pixels
Height : 1 080 pixels
Display aspect ratio : 16:9
Frame rate mode : Variable
Frame rate : 30.292 fps
Minimum frame rate : 18.304 fps
Maximum frame rate : 31.813 fps
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.322
Stream size : 43.6 MiB (98%)
Source stream size : 43.7 MiB (98%)
Title : VideoHandle
Language : English
Encoded date : UTC 2013-09-20 17:59:21
Tagged date : UTC 2013-09-20 17:59:21
mdhd_Duration : 18069

Audio
ID : 2
Format : AAC
Format/Info : Advanced Audio Codec
Format profile : LC
Codec ID : 40
Duration : 18s 346ms
Bit rate mode : Constant
Bit rate : 192 Kbps
Nominal bit rate : 96.0 Kbps
Channel(s) : 1 channel
Channel positions : Front: C
Sampling rate : 48.0 KHz
Compression mode : Lossy
Stream size : 430 KiB (1%)
Title : SoundHandle
Language : English
Encoded date : UTC 2013-09-20 17:59:21
Tagged date : UTC 2013-09-20 17:59:21