When it comes to video quality, a lot of factors are at play. While the quality of an uncompressed video is determined by video resolution, video frame rate and macro block; the quality of compressed videos get impacted by video resolution, bit rate, frame rate, bit control mode, codec, and bit depth. All of these factors are equally important but affect the video quality in varying ways-

• Resolution—

From a digital imaging standpoint, resolution is the same as pixel count of a video. A 1080p video has a resolution of 1920×1080, which is 2,073,600 pixels. However, a 4K video has 3840×2160 or 8,294,400 pixels. So, 4K resolution enhances the details in a video by 4 times. Hence, it’s understandable that higher the resolution of a video, the better its quality.

• Frame Rate—

Video is composed of still images. Images must be displayed at a specific speed to be seen as a video. Frame rate or frame frequency is the measure of the speed in which a video rolls, and is expressed in fps. Fundamentally, frames and images are the same thing.

Note that video quality is not directly affected by frame rate. It determines the fluidity of a video, which then affects the viewing experience. A footage that is stuttering badly does not necessarily suggest that it is a HQ video. A frame rate that is too high or low can cause the video to appear “unnatural”. A proper frame rate will make your video look real, just like how we see motions in real-life.

• Video codec—

Video codec is a video coding format. It refers to the method of video encoding; examples are MP4 H.264 or MP4 HEVC. Each video codec has a different compression algorithm and ratio. It can affect the file size of your output video. Even if all other parameters are identical, a video encoded with HEVC will compress to almost half the size of H.264 or DivX despite having the same quality. Meaning, video encoded with HEVC will look more vivid than H.264 or DivX. A higher compression ratio results in less detail loss and better viewing quality.

MP4 H.264 is the codec format most people choose because of its compatibility and balance between file size and video quality.

• Bit Rate—

Video bit rate refers to the number of bits needed to encode one second of a video. The more bits required to encode a single second of a video, the larger the data processing.

Video file size is determined by bit rate (video size = bitrate x duration). It also affects the video quality. A higher bit rate usually means better video quality. However, there is a diminishing marginal utility effect. This means that if the video quality reaches a certain point, increasing bitrate will result in a larger file size but no improvement in quality.

• Rate control mode—

Rate control mode refers to the method of allocating bits to a frame. The rate control mode selected for your output determines whether your encoder consumes more data to process your video’s most complex parts or keeps it constant for all the frames.

Video encoding allows you to remove unnecessary data and reduce the size of your video files in order to save as many bits as possible for the frames. This is achieved with the help of various rate control modes. However, this process results in data loss and a dip in video quality. Hence, it’s important that you choose the rate control mode carefully in order to control file size and quality. For good quality videos, CRF and 2-pass VBR can be used.

• Bit Depth—

Bit depth (or Color depth) refers to how many bits are used for each component of a color in one pixel. Simply put, bit depth determines how much information can fit into a frame. The majority of digital video formats that we use have 8 bits per channel, and most displays can only support 8 bits at the moment.

The bit depth of a frame determines how fine and smooth the image is. In turn, this affects the quality of the video. A 10-bit video appears to be more vivid than an 8 bit video.