What is it about?
DaVinci Resolve (Studio) video editing applications are highly optimized for hardware acceleration by GeForce RTX graphics cards. These can dramatically reduce the time of some tasks, turning hours into minutes or, for larger projects, days into hours. We’ll take a look at what exactly this is about in a two-part miniseries dedicated to streamlining work in Black Magic Studio video editors with NVIDIA Ada Lovelace GPUs.
If you haven’t been following the field of video compression formats much, you may not know where AV1 came from. This format is an alternative to the lineage of formats developed by the ISO MPEG and ITU JVT consortia that pretty much introduced the mainstream of modern video formats based on block DCT transformation, I, P and B frames with motion prediction, in-loop filters and other tools as we know it. The formats that have emerged from this circle are MPEG-1, MPEG-2, the so-called DivX/XviD (MPEG-4 ASP or also H.263), H.264 (MPEG-4 AVC), H.265 or HEVC, and most recently H.266 or VVC.
However, these formats have traditionally come with usage fees (typically owed by the chip or program manufacturer that uses them) to be paid back to the various companies involved in the development of these technologies and their standardization. This model has long been opposed by the open-source software camp on the one hand, and by large Internet companies on the other, who want video formats with roylty-free usage. AV1 is a product (essentially a competitor) from this part of the video and software industry.
Google first produced the VP8 (acquired as a whole with On2) and VP9 (which it uses on YouTube) formats. These formats are essentially patent-circumventing counterparts to H.264 and H.265, to which they are technologically very similar but are considered somewhat inferior.
After VP9, however, Google in particular again initiated the development of a new format that was already aimed at bringing not only an alternative to HEVC, but potentially a technology more advanced or more powerful in terms of compression. In addition to Google, this time CISCO and other entities (including Mozilla and Xiph for the open-source sphere) were also involved, forming Alliance for Open Media (AOM). The resulting format, like VP8 and VP9, although covered by patents, is not associated with any royalty fees, which is advantageous when used by Internet video services. The reference encoders and specifications are open source.
Genetically, AV1 is mainly based on VP9, but with added “next-gen” compression techniques. While VP9 had fewer tools compared to HEVC and was less complex, the reverse is true for AV1, which purely technologically has more various techniques for prediction (in particular intra prediction has been enhanced, but also inter prediction using motion vectors), more complex in-loop filtering and transformations than HEVC. In AV1, one can see either a next-gen successor to HEVC (i.e. a competitor to VVC) or at least a format half a generation ahead, possibly belonging somewhere between the HEVC and VVC generations (but VVC hasn’t really caught on yet, and Google is also at least prospectively planning a next-generation AV2).
It has to be said that video quality is not just about the format specifications and its compression techniques. Equally important is the ability of the compression software (encoder) to make optimal use of these techniques. Indeed, all possible prediction and quantization modes give a huge space of different combinations among which the encoder has to choose, and this choice is non-trivial. It cannot be guided only by the metrics of similarity between the result and the source, but also by the influence of non-local optimization of the whole image and by psychovisual factors. At the same time, not all possibilities can be explored and shortcuts (early termination of search, skipping some analysis) and approximations must be used. H.264 and HEVC used to be ahead in encoder quality, so even today HEVC can sometimes compete with AV1.
However, when we only consider the area of hardware encoding, there is no longer as expected that an older format (such as HEVC) is favored by a better, more mature encoder against a newer format with less mature software encoders (AV1 with libaom, SVT-AV1). In the area of GPU hardware encoding, the new format should therefore have the potential to immediately improve compression efficiency and thus image quality. That being said, this is also exactly what it should look like when encoding on graphics cards, where the NVENC encoder should achieve a better result when using AV1 (versus HEVC) – better quality at the same bitrate, or lower bitrate at the same quality.
English translation and edit by Jozef Dudáš
- Contents
- What is it about?
- Magic Mask, Smart Reframe
- Face Refinement, Optical Flow and Super Scale
- AV1 and HEVC encoding
- Explore: what is the AV1 video format?
