Comparison of video codecs


Α video codec is software or a device that provides encoding and decoding for digital video, and which may or may not include the use of video compression and/or decompression. Most codecs are typically implementations of video coding formats.
The compression may employ lossy data compression, so that quality-measurement issues become important. Shortly after the compact disc became widely available as a digital-format replacement for analog audio, it became feasible to also store and use video in digital form. A variety of technologies soon emerged to do so. The primary goal for most methods of compressing video is to produce video that most closely approximates the fidelity of the original source, while simultaneously delivering the smallest file-size possible. However, there are also several other factors that can be used as a basis for comparison.

Introduction to comparison

The following characteristics are compared in video codecs comparisons:
The quality the codec can achieve is heavily based on the compression format the codec uses. A codec is not a format, and there may be multiple codecs that implement the same compression specification for example, MPEG-1 codecs typically do not achieve quality/size ratio comparable to codecs that implement the more modern H.264 specification. But quality/size ratio of output produced by different implementations of the same specification can also vary.
Each compression specification defines various mechanisms by which raw video can be reduced in size, from simple bit compression to psycho-visual and motion summarization, and how the output is stored as a bit stream. So long as the encoder component of the codec adheres to the specification it can choose any combination of these methods to apply different parts of the content. The decoder component of a codec that also conforms to the specification recognises each of the mechanisms used, and thus interprets the compressed stream to render it back into raw video for display. Each encoder implements the specification according to its own algorithms and parameters, which means that the compressed output of different codecs will vary, resulting in variations in quality and efficiency between them.
Prior to comparing codec video-quality, it is important to understand that every codec can give a varying degree of quality for a given set of frames within a video sequence. Numerous factors play a role in this variability. First, all codecs have a bitrate control mechanism that is responsible for determining the bitrate and quality on a per-frame basis. A difference between variable bitrate and constant bitrate creates a trade-off between a consistent quality over all frames, on the one hand, and a more constant bitrate, which is required for some applications, on the other. Second, some codecs differentiate between different types of frames, such as key frames and non-key frames, differing in their importance to overall visual quality and the extent to which they can be compressed. Third, quality depends on prefiltrations, which are included on all present-day codecs. Other factors may also come into play.
For a sufficiently long clip, it is possible to select sequences that have suffered little from the compression, and sequences that have suffered heavily, especially if CBR has been used, whereby the quality between frames can vary highly due to different amounts of compression needed to achieve a constant bitrate. So, in a given long clip, such as a full-length movie, any two codecs may perform quite differently on a particular sequence from the clip, while the codecs may be approximately equal in quality over a wider sequence of frames. Press-releases and amateur forums may sometimes select sequences known to favor a particular codec or style of rate-control in reviews.

Objective video quality

Objective video evaluation techniques are mathematical models that seek to predict human judgments of picture quality, as often exemplified by the results of subjective quality assessment experiments. They are based on criteria and metrics that can be measured objectively and automatically evaluated by a computer program. Objective methods are classified based on the availability of an original pristine video signal, which is considered to be of high quality. Therefore, they can be classified as:
This is concerned with how video is perceived by a viewer, and designates their opinion on a particular video sequence. Subjective video quality tests are quite expensive with regard to time and human resources.
There are many ways of showing video sequences to experts and recording their opinions. A few of them have been standardized, mainly in and .
The reason for measuring subjective video quality is the same as for measuring the mean opinion score for audio. Opinions of experts can be averaged and the average mark stated as, or accompanied by, a given confidence interval. Additional procedures can be used for averaging. For example, experts whose opinions are considered unstable may have their opinions rejected.
In the case of video codecs, this is a very common situation. When codecs with similar objective results show results with different subjective results, the main reasons can be:
It is difficult to use long sequences for subjective testing. Commonly, three or four ten-second sequences are used, while full movies are used for objective metrics. Sequence selection is important those sequences that are similar to the ones used by developers to tune their codecs are more competitive.

Performance comparison

Speed comparison

Number of frames per second commonly used for compression/decompression speed measurement.
The following issues should be considered when estimating probable codec performance differences:
So, for example, codec A may, on modern computers, give slower performance than codec B. Meanwhile, the same pair of codecs may give opposite results if running on an older computer with reduced memory resources.

Profiles support

Modern standards define a wide range of features and require very substantial software or hardware efforts and resources for their implementation. Only selected profiles of a standard are typically supported in any particular product.
The H.264 standard includes the following seven sets of capabilities, which are referred to as profiles, targeting specific classes of applications:
The standard also contains four additional all-Intra profiles, which are defined as simple subsets of other corresponding profiles. These are mostly for professional applications:
Moreover, the standard now also contains three Scalable Video Coding profiles.
An accurate comparison of codecs must take the profile variations within each codec into account.
See also MPEG-2 Profiles and Levels.

Supported rate control strategies

Videocodecs' rate control strategies can be classified as:
Variable bitrate is a strategy to maximize the visual video quality and minimize the bitrate. On fast-motion scenes, a variable bitrate uses more bits than it does on slow-motion scenes of similar duration, yet achieves a consistent visual quality. For real-time and non-buffered video streaming when the available bandwidth is fixed e.g. in videoconferencing delivered on channels of fixed bandwidth a constant bitrate must be used.
CBR is commonly used for videoconferences, satellite and cable broadcasting. VBR is commonly used for video CD/DVD creation and video in programs.
Bit rate control is suited to video streaming. For offline storage and viewing, it is typically preferable to encode at constant quality rather than using bit rate control.

Software characteristics

Codecs list

The Xiph.Org Foundation has negotiated an irrevocable free license to Theora and other VP3-derived codecs for everyone, for any purpose.
DivX Plus is also known as DivX 8. The latest stable version for Mac is DivX 7 for Mac.

Native operating system support

Note that operating system support does not mean whether video encoded with the codec can be played back on the particular operating system for example, video encoded with the DivX codec is playable on Unix-like systems using free MPEG-4 ASP decoders, but the DivX codec is only available for Windows and macOS.
CodecmacOSother Unix & Unix-likeWindows
3ivx
Blackbird
Cinepak
DivX
FFmpeg
RealVideo
Schrödinger
Sorenson Video 3
Theora
x264
Xvid
Elecard

Technical details

Theora streams with different frame rates can be chained in the same file, but each stream has a fixed frame rate.

Freely available codecs comparisons

List of freely available comparisons and their content description:
Name of comparisonType of comparisonDate of publicationList of compared codecsComments
Series of subjective comparison of popular codecs
  • 2002
  • 2003
  • 2005
  • DivX4.12, On2 VP3, XviD 1/25 and WMV8 and DivX5.01, XviD 3/27 and ON2 VP4 at first version
  • Dirac, Elecard AVC HP, libavcodec MPEG-4, NeroDigital ASP, QuickTime 7, Snow, Theora, VideoSoft H.264 HP, XviD 1.1 beta 2 in last one
    		• Subjective comparison with convenient visualization
    Series of objective HEVC/AV1 codecs comparisons
  • 2015 Oct.
  • 2016 Aug.
  • 2017 Sept.
  • 2018 Sept.
  • 2015: f265 H.265 Encoder, Intel MSS HEVC GAcc, Intel MSS HEVC Software, Ittiam HEVC Hardware Encoder, Ittiam HEVC Software Encoder, Strongene Lentoid HEVC Encoder, SHBP H.265 Real time encoder, x265, InTeleMax TurboEnc, SIF Encoder, VP9 Video Codec, x264
  • 2016: Chips&Media HEVC Encoder, Intel MSS HEVC Encoder, Kingsoft HEVC Encoder, nj265, SHBPH.265 Real time encoder, x265, nj264, x264
  • 2017: Kingsoft HEVC Encoder, nj265, NVIDIA NVENC SDK, Telecast, x265, AV1, nj264, SIF encoder, uAVS2, VP9, x264
  • 2018: HW265, Intel MFX, Intel MFX, Kingsoft HEVC Encoder, sz265, Tencent Shannon Encoder, UC265, VITEC HEVC GEN2+, x265, AV1, SIF encoder, sz264, VP9, x264
    		• Detailed objective comparisons
    Series of objective H.264 codecs comparisons with MPEG-4 ASP reference
  • 2004
  • 2005 Jan.
  • 2005 Dec.
  • 2006 Dec.
  • 2007 Dec.
  • 2009 May
  • 2010 Apr.
  • 2011 May
  • 2012 May
  • 2013 Dec.
  • 2005 : Mpegable AVC, Moonlight H.264, MainConcept H.264, Fraunhofer IIS, Ateme MPEG-4 AVC/H.264, Videosoft H.264, DivX Pro 5.1.1
  • 2005 : DivX 6.0, ArcSoft H.264, Ateme H.264, ATI H.264, Elecard H.264, Fraunhofer IIS H.264, VSS H.264, x264
  • 2006: DivX 6.2.5, MainConcept H.264, Intel H.264, VSS H.264, x264, Apple H.264,, Sorenson H.264
  • 2007: XviD, MainConcept H.264, Intel H.264, x264, AMD H.264, Artemis H.264
  • 2009: XviD, Dicas H.264, Elecard H.264, Intel IPP H.264, MainConcept H.264, x264
  • 2010: XviD, DivX H.264, Elecard H.264, Intel MediaSDK AVC/H.264, MainConcept H.264, Microsoft Expression, Encoder, Theora, x264
  • 2011: DivX H.264, Elecard H.264, Intel SandyBridge Transcoder, MainConcept H.264, MainConcept H.264, Microsoft Expression Encoder, DiscretePhoton, x264, VP8, XviD
  • 2012: DivX H.264, Elecard H.264, Intel Ivy Bridge QuickSync, MainConcept H.264, MainConcept H.264, MainConcept H.264, DiscretePhoton, x264, XviD
    		• Detailed objective comparisons
    Two size and time comparisons of lossless codecs
  • 2004 Oct.
  • 2007 Mar.
  • 2004 : Alpary v2.0, AVIzlib v2.2.3, CamStudio GZIP v1.0, CorePNG v0.8.2, FFV1 ffdshow 08/08/04, GLZW v1.01, HuffYUV v2.1.1, Lagarith v1.0.0.1, LEAD JPEG v1.0.0.1, LOCO v0.2, MindVid v1.0 beta 1, MSUlab beta v0.2.4, MSUlab v0.5.2, PicVideo JPEG v.2.10.0.29, VBLE beta
  • 2007 : Alpary, ArithYuv, AVIzlib, CamStudio GZIP, CorePNG, FastCodec, FFV1, Huffyuv, Lagarith, LOCO, LZO, MSU Lab, PICVideo, Snow, x264, YULS
    		• in 2007 more detailed report with new codecs including first standard H.264
    Objective comparison of MPEG-4 codecs
  • 2005 Mar.
    		• DivX 5.2.1, DivX 4.12, DivX 3.22, MS MPEG-4 3688 v3, XviD 1.0.3, 3ivx D4 4.5.1, OpenDivX 0.3Different versions of DivX were also compared. The Xvid results may be erroneous, as deblocking was disabled for it while used for DivX.
    Scientifically accurate subjective comparison using 50 experts and SAMVIQ methodology
  • 2006 Feb.
    		• DivX 6.0, Xvid 1.1.0, x264, WMV 9.0 PSNR via VQM via SSIM comparison was also done
    Objective MPEG-2 Decoders comparison
  • 2006 May.
    		• bitcontrol MPEG-2 Video Decoder, DScaler MPEG2 Video Decoder, Elecard MPEG-2 Video Decoder, ffdshow MPEG-4 Video Decoder, InterVideo Video Decoder, Ligos MPEG Video Decoder, MainConcept MPEG Video Decoder, Pinnacle MPEG-2 DecoderObjectly tested decoders "crash test"
    Personal subjective opinion
  • 2003 Nov.
    		• 3ivx, Avid AVI 2.02, Cinepak, DivX 3.11, DivX 4.12, DivX 5.0.2, DV, Huffyuv, Indeo 3.2, Indeo 4.4, Indeo 5.10, Microsoft MPEG-4 v1, Microsoft MPEG-4 v2, Microsoft RLE, Microsoft Video 1, XviD, 3ivx, Animation, Blackmagic 10-bit, Blackmagic 8-bit, Cinepak, DV, H.261, H.263, Motion-JPEG, MPEG-4 Video, PNG, Sorenson Video, Sorenson Video 3Sometimes comparison is short
    Scientific paper
  • 2009 Mar.
    		• Dirac, Dirac Pro, Theora I, H.264, Motion JPEG2000 Quite detailed comparison of software available in Q2-2008; However, a buggy version of ffmpeg2Theora was used
    Objective and subjective quality comparison of VP8 and x264
  • 2010 Jun.
    		• VP8, x264VQM, SSIM and PSNR for 19 CIF video clips with bitrates of 100, 200, 500 and 1000 kbit/s