Which Frame Rate is Right For Me?

I’m sure a lot of you are shooting with DV or HDV cameras that have a few frame rates and interlace options available. I know I do. They make nice pictures and give you a lot of versatility. This versatility is also an opportunity to make mistakes. Most of these cameras have 3-4 options. 59.94i, 29.97p, 23.98p, and maybe 23.98p (advanced). Good god so many numbers and letters. I won’t go into too much depth in this post about the intricacies of these formats, but I will briefly go over each.

  • 59.94i:  Consists of 2 sets of fields per frame at 59.94 fields per second, or 29.97 frames per second. The i stands for interlaced.
  • 29.97p: Consists of 29.97 frames per second. The p stands for progressive, so each frame is one image, there is no interlacing.
  • 23.98p: Consists of 23.98 frames per second, progressive. These 23.98 frames per second are then on most cameras recorded to tape at 59.94i. The 23.98p is converted to 59.94i in a process called 3:2 pulldown. Each frame is converted to fields and stored as interlaced video with some fields repeated to make up the approximately 12 field difference. This is the same process used to transfer 24 frame film to NTSC video.
  • 23.98p (advanced): The same as the 23.98p above except with a different 3:2 pulldown pattern that is more efficiently compressed in the camera and easier for computers to process the 59.94i to 23.98p.

You are about to start a project, so which one do you choose? Well, it depends on what your goal for the project is. Are you aiming for broadcast, web, DVD, download, or theatrical? The only one of these that you should even consider 59.94i for is broadcast. But even then I would recommend 29.97p because so many people have LCD and Plasma TVs these days, and neither are capable of displaying interlaced material, they have to deinterlace it first, which degrades the image. In fact the only displays that can correctly display interlace are CRTs; good old tube televisions. So lets forget about 59.94i. So should you shoot 29.97p or 23.98p (advanced). I would not recommend standard 23.98 for most projects, more on that in a second. If broadcast is your main goal than you should definitely choose 29.97p. If you need to playback from tape than 29.97p would be preferable unless you were to bump it up or over to HDCAM 23.98p. This is the case because DVCAM and Digibeta do not support 23.98p, they would have to be played back as a 3:2 pulldowned 59.94i, which would then be deinterlaced in order to be displayed on an LCD, plasma, or projector. Deinterlacing is the last thing you want done to your video. If your aim is anything other than broadcast 23.98p is a front runner. The only time I would recommend 29.97p over 23.98p aside from broadcast and tape playback would be if you were shooting sports, or other high action material, because you get a greater range of pan speeds without judder.

So what is so great about 23.98p (advanced), or 23.98pa for short? There are advantages to 23.98pa other than it’s sounding cool. Lets start with web streaming or download. When encoding for streaming or download file size is very important because each bit costs you bandwidth and costs the viewer time to download or buffer. At 23.98pa you can get better quality at the same bitrate versus 29.97p because the encoder can allocate more bits per frame because there are fewer of them, which means you can encode your material into smaller files or better quality. The same is true for DVD, which is important if you want to include a lot of material on the DVD.

And finally if you are aiming for a theatrical release 23.98pa can help you in many ways. There are more ways to release your movie than 5 years ago. Your options include DVD, tape, digital server, and film print. The DVD advantage we already covered. And tape playback we covered. That leaves digital server playback, and film print playback. Film prints play at 24p so moving from 23.98pa is a simple .001 speedup. The audio will have to be sped up as well, but this is something post houses do all the time. To go from 29.97p to 24p would require very intensive frame rate conversion that degrades the image quality and is very expensive. Digital server playback requires your video to be encoded, and once again you benefit from being able to allocate more bits per frame. For digital server playback there is another benefit from having your material at 23.98pa. Hollywood’s digital specification only allows 24p playback. Despite this being completely ridiculous there is no getting around it for now. So the conversion to this spec, known as DCI, is basically the same as the conversion needed for making a film print.

So why is the advanced 23.98p better than the standard 23.98p? It has to do with the way that your camera compresses the image. In the standard mode there are times when a frame is split into only 2 mixed fields, that is there are 24p frames that are split into field 2 of frame 1 and field 1 of frame 2, which due to the way DV is compressed leads to the bleeding of other frames into this mixed field frame. If you want to learn more there is a good write up here.

So in short 23.98p is helpful in the greatest number of situations, but if you are stuck in broadcast or standard def tape playback 29.97p is the way to go.