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asdfasa60504448
asdfasa60504448
Participant
October 3, 2017
Answered

Too big bitrates after transcoding to CineForm?

  • October 3, 2017
  • 1 reply
  • 2433 views

Hello,

After transcoding h.264 29,97 fps (100 Mbps) UHD footage to CineForm YUV 10 bit Film Scan (Quality=4) codec, new video files bitrates varies from 600 Mbps to 1200 Mbps?

For me it seems 2-3 times bigger than compared to these sources:

https://blog.frame.io/2017/02/13/50-intermediate-codecs-compared/

and AJA DataCalc app. Based by sources CineForm 4:2:2 bitrate should be about 380 Mbps. Video properties of one transcoded file:

Type: QuickTime Movie

File Size: 1,38 GB

Image Size: 3840 x 2160

Frame Rate: 29,99

Source Audio Format: 48000 Hz - 16 bit - Stereo

Project Audio Format: 48000 Hz - 32 bit floating point - Stereo

Total Duration: 00;00;13;22

Pixel Aspect Ratio: 1,0

QuickTime Details:

Movie contains 1 video track(s), 1 audio track(s), 0 closed caption track(s), and 1 timecode track(s).

Video:

There are 413 frames with a duration of 50/1499ths.

Video track 1:

Duration is 0;00;13;23

Average frame rate is 29,99 fps

Video track 1 contains 1 type(s) of video data:

Video data block #1:

Frame Size = 3840 x 2160

Compressor = GoPro CineForm

Quality = Most (5,00)

Audio:

Audio track 1 contains 1 type(s) of audio data:

Audio data block #1:

Format = 16 bit - Stereo

Rate = 48000 Hz

Compressor = 16-bit Little Endian

Timecode:

Timecode track 1 contains 1 type(s) of data:

Timecode data block #1:

Start Time = 00;00;00;00

Reel name =

VR Projection: None

There is strange parameter for me "Quality = Most (5,00)". Doesn't matter if I change codec quality from 2 to 5, it is always 5. But if I set quality to 5 (Film Scan 2), transcoded video file bitrate almost doubles. At lower quality settings, for example quality=2, video bitrates decreases but are still even bigger than described CineForm 4:2:2 bitrate (380 Mbps).

This topic has been closed for replies.
Correct answer excited_Genie16B8

Maybe average bitrates...are 2-3 times smaller than mine because they use completely different footage...

A valid assumption.  ProRes is a variable bitrate codec with a maximum, and DNx is a fixed bitrate codec.

So with Cineform, if a frame needs 30 bits, it'll get all 30 bits, whereas ProRes and DNx will limit the bitrate to 20, thus reducing quality.  But if a scene only needs 10 bits, then Cineform will use 10 bits.  ProRes will also use 10 bits, but DNx will still be using 20 bits, thus making the file unnecessarily larger.

So with Cineform, you do get the best quality/size ratio.  ProRes has the potential to be lesser quality, and DNx has the potential to be both lesser quality and larger files.

All of this depends, of course, on the source material.

1 reply

E
excited_Genie16B8
Legend
October 3, 2017

The best part about Cineform is that it's a Constant Quality codec.  That means it will use whatever bits it needs to hit the target quality.  There is no bitrate target, only a quality target.

asdfasa60504448
asdfasa60504448Author
Participant
October 3, 2017

Thank you for explanation. Now it is clearer. Maybe average bitrates on earlear written sources (https://blog.frame.io/2017/02/13/50-intermediate-codecs-compared/ and AJA DataCalc app) are 2-3 times smaller than mine because they use completely different footage...

I think the confusion is due to some users say CineForm has lower bitrate than ProRes 422 HQ or DNxHR HQ but quality is similar (or even better). My example is oposite. Footage transcoded to CineForm has even bigger bitrate.

E
excited_Genie16B8Correct answer
Legend
October 3, 2017

Maybe average bitrates...are 2-3 times smaller than mine because they use completely different footage...

A valid assumption.  ProRes is a variable bitrate codec with a maximum, and DNx is a fixed bitrate codec.

So with Cineform, if a frame needs 30 bits, it'll get all 30 bits, whereas ProRes and DNx will limit the bitrate to 20, thus reducing quality.  But if a scene only needs 10 bits, then Cineform will use 10 bits.  ProRes will also use 10 bits, but DNx will still be using 20 bits, thus making the file unnecessarily larger.

So with Cineform, you do get the best quality/size ratio.  ProRes has the potential to be lesser quality, and DNx has the potential to be both lesser quality and larger files.

All of this depends, of course, on the source material.

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