Video compression choices

[harrisonfree]

I found your site through this link: https://forum.videohelp.com/threads/384727-Can-anyone-say-which-tool-method-use-to-con...e-2-vid-files-!!! and have a similar question.

I have been given two versions of a video and am trying to figure out how the smaller file was created. Like the link poster, I was able to collect their MediaInfo details, which are:


1) Smaller File:

General
Complete name : small_XXX.mp4
Format : MPEG-4
Format profile : Base Media
Codec ID : isom (isom/iso2/avc1/mp41)
File size : 375 MiB
Duration : 1 h 2 min
Overall bit rate : 841 kb/s
Writing application : Lavf57.71.100

Video
ID : 2
Format : AVC
Format/Info : Advanced Video Codec
Format profile : Main@L3.1
Format settings : CABAC / 4 Ref Frames
Format settings, CABAC : Yes
Format settings, ReFrames : 4 frames
Codec ID : avc1
Codec ID/Info : Advanced Video Coding
Duration : 1 h 2 min
Bit rate : 705 kb/s
Width : 872 pixels
Height : 486 pixels
Display aspect ratio : 16:9
Frame rate mode : Constant
Frame rate : 30.000 FPS
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.055
Stream size : 314 MiB (84%)
Writing library : x264 core 148
Encoding settings : cabac=1 / ref=4 / deblock=1:0:0 / analyse=0x1:0x111 / me=hex / subme=7 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=0 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=15 / lookahead_threads=2 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=3 / b_pyramid=2 / b_adapt=1 / b_bias=0 / direct=1 / weightb=1 / open_gop=0 / weightp=2 / keyint=120 / keyint_min=12 / scenecut=40 / intra_refresh=0 / rc_lookahead=40 / rc=crf / mbtree=1 / crf=22.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / ip_ratio=1.40 / aq=1:1.00
Language : English
Color range : Limited
Color primaries : BT.601 NTSC
Transfer characteristics : BT.709
Matrix coefficients : BT.601
Codec configuration box : avcC

Audio
ID : 1
Format : AAC LC
Format/Info : Advanced Audio Codec Low Complexity
Codec ID : mp4a-40-2
Duration : 1 h 2 min
Bit rate mode : Constant
Bit rate : 128 kb/s
Channel(s) : 2 channels
Channel layout : L R
Sampling rate : 48.0 kHz
Frame rate : 46.875 FPS (1024 SPF)
Compression mode : Lossy
Stream size : 57.1 MiB (15%)
Language : English
Default : Yes
Alternate group : 1



2) Larger File:

General
Complete name : large_XXX.mp4
Format : MPEG-4
Codec ID : M4V (isom/avc1/mp42)
File size : 1.35 GiB
Duration : 1 h 2 min
Overall bit rate mode : Variable
Overall bit rate : 3 105 kb/s
Encoded date : UTC 2019-11-29 04:23:18
Tagged date : UTC 2019-11-29 04:23:18

Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : Main@L3.1
Format settings : CABAC / 3 Ref Frames
Format settings, CABAC : Yes
Format settings, ReFrames : 3 frames
Codec ID : avc1
Codec ID/Info : Advanced Video Coding
Duration : 1 h 2 min
Bit rate mode : Constant
Bit rate : 3 000 kb/s
Maximum bit rate : 7 336 kb/s
Width : 1 280 pixels
Height : 720 pixels
Display aspect ratio : 16:9
Frame rate mode : Constant
Frame rate : 30.000 FPS
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.109
Stream size : 1.31 GiB (97%)
Encoded date : UTC 2019-11-29 04:23:18
Tagged date : UTC 2019-11-29 04:23:18
Color range : Limited
Color primaries : BT.601 NTSC
Transfer characteristics : BT.709
Matrix coefficients : BT.601
Codec configuration box : avcC

Audio
ID : 2
Format : AAC LC
Format/Info : Advanced Audio Codec Low Complexity
Codec ID : mp4a-40-2
Duration : 1 h 2 min
Bit rate mode : Variable
Bit rate : 96.0 kb/s
Maximum bit rate : 99.9 kb/s
Channel(s) : 2 channels
Channel layout : L R
Sampling rate : 48.0 kHz
Frame rate : 46.875 FPS (1024 SPF)
Compression mode : Lossy
Stream size : 42.8 MiB (3%)
Language : English
Encoded date : UTC 2019-11-29 04:23:18
Tagged date : UTC 2019-11-29 04:23:18



The content is identical. I made the file names more specific for the sake of clarity. The smaller file was made (or is dated) about a year and a half before the larger file. My computer is old and slow so I tend to view these on the TV from a USB stick. I don't understand why the large file has to be over 3 times the size of the small file when they look and sound pretty comparable to me. Based on the MediaInfo, it even looks like the audio on the smaller file is higher quality. I am afraid I am being left behind with my older system as these file sizes grow exponentially and want to keep it as functional as long as I can.

Ultimately, I guess I am asking how one would go about turning the larger file into the smaller file on a Mac?

[jagabo]

The smaller file was encoded with x264. The settings are listed. They correspond to the medium preset at CRF 22. except for keyint=120 and keyint_min=12. Any tool that uses the x264 will work. Most free tools use x264, Handbrake, for example.

But the smaller file also uses a much smaller frame size, 872x486 vs. 1280x720 (Handbrake can downscale like this). The smaller frames require fewer bits, hence a smaller file. But that's treading off resolution to get a smaller file.

[Cornucopia]

Know that if you attempt to take the larger one and reduce it, you will be lossily re-encoding with some accompaying loss of quality. Probably not worth the effort, if you are already ok with the smaller one.

Scott

[harrisonfree]

Hi guys,

Thanks for the insight. I will look at the two versions of this file more closely before deciding whether to proceed. I'm more interested in being able to archive other examples more efficiently that I only have at the higher resolution/larger file size since they eat up so much real estate at their full size. Much appreciated.

Forgot, one other question: Is it only the smaller frame size that accounts for the difference in file size?

[sophisticles]

Forgot, one other question: Is it only the smaller frame size that accounts for the difference in file size?

The smaller frame size requires less bit rate in order to achieve a similar bit/pixel ratio.

The 1280x720 has a ratio of Bits/(Pixel*Frame) : 0.109

The 872x486 has a ratio of Bits/(Pixel*Frame) : 0.055

Not taking into account the difference in frame size, the larger file has roughly twice the quality per pixel than the smaller file, on a larger monitor or TV chances are you would notice the quality difference.

[jagabo]

Forgot, one other question: Is it only the smaller frame size that accounts for the difference in file size?

No, the lower bitrate accounts for the smaller file size. The smaller frame size allows for fewer compression artifacts at that lower bitrate. But again, you're trading off resolution to get fewer compression artifacts. If you view both of the videos full screen you'll see that the smaller video is not as sharp. Taking this to the extreme, you could reduce the resolution to 1x1 pixel and save with no compression at all and get a tiny file. But viewing that video wouldn't be very interesting.

There may also be differences in the codecs. Not all h.264 encoders are created equal. And not all settings deliver the same quality at the same bitrate.