I find it very annoying when many people, especially even industry professionals, get very misinformed about the video recording technology developed by manufacturers or by any means of technology hype.
I have a buddy who is an experienced video cameraman, and I think he blindly spent close to $6k on a highly compressed video format when he could have spent a bit more to get a camera with lesser compression that will yield better quality in the footage acquisition.
It's been a while since I posted any info-sharing thread, so here goes my contribution.
I'm sure there are many more info on the web, but the gist is this:
What is Video Compression?
It is to save storage space in your video image, much akin to how JPEG file vs. a TGA/RAW photo file.
What does it do?
Video compression discards data (Luminance, Chrominance &/or motion) based on an algorithm that predicts and thinks what the human eye will not see or notice. Different compression technology have it's own algorithm to discard these video data, but compression can be classified generally into two categories. Color Space recording capability, and Interframe Compression vs. Intraframe Compression.
Color Space
Color space determines the amount of color info being recorded in the video. It is expressed in ratios seen like 4:4:4, 4:2:0 vs. 4:2:2. Video is generally split into 3 channels, the Y (Luminance), R-Y & B-Y. In the true 4:4:4 color space recording, every data in a 4-pixel block is recorded pixel for pixel without any interpolation like the other type does.
Further Reading:
http://en.wikipedia.org/wiki/Chroma_subsampling
http://en.wikipedia.org/wiki/YUV
http://www.usa.canon.com/dlc/controller?act=GetArticleAct&articleID=3389
Intraframe vs. Interframe Compression
Intraframe compression is compressing every video frame like what JPEG does to a still photo. Benefits of this type of compression is that it preserves motion data very well, and is very well suited for chroma keying applications. Downside is that the video file sizes are bigger.
Interframe compression take motion into consideration and in a group of frames, the algorithm involves taking a key reference frame (the i-Frame, aka Intra-frame), and it predicts the motion and discards information along the way. Interframe compression can produce very efficient filesizes, but may not be good for certain applications, eg. sports, fast action & chroma-keying. In the not-so-earlier days of computing, it is also more intensive for the CPU to process Interframe based video files for decoding & re-encoding.
Examples of Interframe based compression
MPEG, MPEG2, H.264, MXF as file formats.
MPEG-IMX, BetacamSX, XDCAM, HDV, XDCAM HD, XDCAM 422, XDCAM EX, Canon XF, and AVCHD as camera recording formats.
Examples of Intraframe based compression
Uncompressed 10bit/8bit 422 Quicktime, ProRES422, DVCPro50, DVCProHD as file formats.
miniDV, DVCAM, DVCPro25, DVCPro50, DVCproHD, AVC-Intra50, and AVC-Intra100 as camera formats.
The holy-grail of high quality video is still Digital Betacam for Standard Definition, and HDCAM for High Definition at 1440x1080 or even HDCAM SR for Full HD at 1920x1080.
These camera formats can be considered as a reference for almost no compression at 4:2:2 color space, although in technical specification, there are still some compression involved. (DCT compression)
High end formats like RED ONE, Arri Alexa, etc.. are in the league of raw 4:4:4 color space and higher than 2K recording capabilities.
So in summary for the layman....
The smaller your file size, the more compression you have in your video.
The more info you discard, the lousier your video quality is going to be in terms of color, image sharpness, motion artifacts & compression noise / image blockiness.
Here's the files size comparison:
- 60mins of HDCAM uncompressed 10bit 4:2:2 1080i25 video file is taking up almost 500GB of space
- 60mins of ProRES HQ 1080i25 video eats up 100GB
- 60mins of DVCProHD / AVC-Intra100 1080i25 video gobbles up 60GB
- 60mins of Canon XF 50mbps 1080i25 video uses up about 30GB of space
- 60mins of XDCAM HD 35mbps 1080i25 video takes up about 20GB of space
- 60mins of HDV 1080i25 video takes about 13GB
- 60mins of AVCHD 1080i25 video takes about 5GB
Here's a rough price comparison of pro video cameras:
- HDCAM cameras above $80k range
- ProRES recorders about $7k range (no cameras other than Arri Alexa)
- DVCProHD/AVC-Intra cameras $8k & above
- XF cameras $10k and above
- XDCAM cameras $7k & above
- HDV cameras $6k range
- AVCHD cameras $4k range
Conclusion
Like MP3 vs. uncompressed CD audio, JPEG vs. RAW files, some people are just happy to have smaller & manageable files at a compromise over quality.
Compression is not a bad thing, and as compression technology gets more efficient, we're able to attain the best of both worlds in our video recording. There's always an application for every technology and as people who loves dabbling with video as a hobby or as a pro, we'll need to understand the limitations and advantages of our tools & equipment.
Don't be hyped into buying some video equipment just because it promises larger sensors, and bigger lenses because ultimately the limitation and bottleneck is still the recording format.
I believe MPEG2 & AVCHD have been the recent popular video acquisition format mainly because broadcasters have adopted native MPEG2 & H264 files for tapeless & server-based transmission. It is no doubt that these formats are good delivery format, but not necessarily a good acquisition format.
:thumbsup:
2 cents worth of info that I hope is useful for CS videographers.
Feel free to add more info to this thread pertaining to Video compression and type of video formats.
________
ROMULUS ENGINE
I have a buddy who is an experienced video cameraman, and I think he blindly spent close to $6k on a highly compressed video format when he could have spent a bit more to get a camera with lesser compression that will yield better quality in the footage acquisition.
It's been a while since I posted any info-sharing thread, so here goes my contribution.
I'm sure there are many more info on the web, but the gist is this:
What is Video Compression?
It is to save storage space in your video image, much akin to how JPEG file vs. a TGA/RAW photo file.
What does it do?
Video compression discards data (Luminance, Chrominance &/or motion) based on an algorithm that predicts and thinks what the human eye will not see or notice. Different compression technology have it's own algorithm to discard these video data, but compression can be classified generally into two categories. Color Space recording capability, and Interframe Compression vs. Intraframe Compression.
Color Space
Color space determines the amount of color info being recorded in the video. It is expressed in ratios seen like 4:4:4, 4:2:0 vs. 4:2:2. Video is generally split into 3 channels, the Y (Luminance), R-Y & B-Y. In the true 4:4:4 color space recording, every data in a 4-pixel block is recorded pixel for pixel without any interpolation like the other type does.
Further Reading:
http://en.wikipedia.org/wiki/Chroma_subsampling
http://en.wikipedia.org/wiki/YUV
http://www.usa.canon.com/dlc/controller?act=GetArticleAct&articleID=3389
Intraframe vs. Interframe Compression
Intraframe compression is compressing every video frame like what JPEG does to a still photo. Benefits of this type of compression is that it preserves motion data very well, and is very well suited for chroma keying applications. Downside is that the video file sizes are bigger.
Interframe compression take motion into consideration and in a group of frames, the algorithm involves taking a key reference frame (the i-Frame, aka Intra-frame), and it predicts the motion and discards information along the way. Interframe compression can produce very efficient filesizes, but may not be good for certain applications, eg. sports, fast action & chroma-keying. In the not-so-earlier days of computing, it is also more intensive for the CPU to process Interframe based video files for decoding & re-encoding.
Examples of Interframe based compression
MPEG, MPEG2, H.264, MXF as file formats.
MPEG-IMX, BetacamSX, XDCAM, HDV, XDCAM HD, XDCAM 422, XDCAM EX, Canon XF, and AVCHD as camera recording formats.
Examples of Intraframe based compression
Uncompressed 10bit/8bit 422 Quicktime, ProRES422, DVCPro50, DVCProHD as file formats.
miniDV, DVCAM, DVCPro25, DVCPro50, DVCproHD, AVC-Intra50, and AVC-Intra100 as camera formats.
The holy-grail of high quality video is still Digital Betacam for Standard Definition, and HDCAM for High Definition at 1440x1080 or even HDCAM SR for Full HD at 1920x1080.
These camera formats can be considered as a reference for almost no compression at 4:2:2 color space, although in technical specification, there are still some compression involved. (DCT compression)
High end formats like RED ONE, Arri Alexa, etc.. are in the league of raw 4:4:4 color space and higher than 2K recording capabilities.
So in summary for the layman....
The smaller your file size, the more compression you have in your video.
The more info you discard, the lousier your video quality is going to be in terms of color, image sharpness, motion artifacts & compression noise / image blockiness.
Here's the files size comparison:
- 60mins of HDCAM uncompressed 10bit 4:2:2 1080i25 video file is taking up almost 500GB of space
- 60mins of ProRES HQ 1080i25 video eats up 100GB
- 60mins of DVCProHD / AVC-Intra100 1080i25 video gobbles up 60GB
- 60mins of Canon XF 50mbps 1080i25 video uses up about 30GB of space
- 60mins of XDCAM HD 35mbps 1080i25 video takes up about 20GB of space
- 60mins of HDV 1080i25 video takes about 13GB
- 60mins of AVCHD 1080i25 video takes about 5GB
Here's a rough price comparison of pro video cameras:
- HDCAM cameras above $80k range
- ProRES recorders about $7k range (no cameras other than Arri Alexa)
- DVCProHD/AVC-Intra cameras $8k & above
- XF cameras $10k and above
- XDCAM cameras $7k & above
- HDV cameras $6k range
- AVCHD cameras $4k range
Conclusion
Like MP3 vs. uncompressed CD audio, JPEG vs. RAW files, some people are just happy to have smaller & manageable files at a compromise over quality.
Compression is not a bad thing, and as compression technology gets more efficient, we're able to attain the best of both worlds in our video recording. There's always an application for every technology and as people who loves dabbling with video as a hobby or as a pro, we'll need to understand the limitations and advantages of our tools & equipment.
Don't be hyped into buying some video equipment just because it promises larger sensors, and bigger lenses because ultimately the limitation and bottleneck is still the recording format.
I believe MPEG2 & AVCHD have been the recent popular video acquisition format mainly because broadcasters have adopted native MPEG2 & H264 files for tapeless & server-based transmission. It is no doubt that these formats are good delivery format, but not necessarily a good acquisition format.
:thumbsup:
2 cents worth of info that I hope is useful for CS videographers.
Feel free to add more info to this thread pertaining to Video compression and type of video formats.
________
ROMULUS ENGINE
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