莫斯科国家报告:俄罗斯仍是普京的首选.264，但对HEVC和AV1有影响

Every year the Moscow State University (MSU) Graphics and Media Lab releases multiple codec comparisons that are essential reading for any company that delivers streaming video to its viewers. 今年, 密歇根州立大学发布了三份报告，我在下面详细介绍, 所有这些都是免费下载的，其中包含数据快照, 和完整的企业报告三份报告的所有数据950美元.

All reports evaluate multiple codecs of different types using two use cases—offline encoding (1 fps) and online encoding (30 fps)—with the number of test clips and objective metrics deployed varying by report. 第一份报告，第一部分:全高清，客观于2020年7月发布，测试了代表H.265 av1 h.264, 和其他编解码器, 有50个全高清视频, 并为SSIM报告结果, VMAF, PSNR日志和平均MSE, 以及使用SSIM作为度量的最佳质量/速度权衡.

表1 shows what you get in the free version as compared to the enterprise version, with some overall details also provided in the online report description linked to above. 企业版有很多价值, including the encoder settings used for the tests which are created with input from each developer.

表1. 免费版和企业版都有什么

图1 shows the VMAF ratings for all tested codecs using the x265 codec as the reference at 100%. Codecs to the left can deliver the same quality as x265 at the data rate shown in the chart, 所以BVC2.0 codec offers a 25% bitrate reduction at the same quality while the Aurora AV1 Encoder offers a 19% reduction. Codecs to the right of x265 need a higher data rate to deliver the same quality, so the rav1e AV1 encoder needs 37% more data to deliver x265 quality, 比奥罗拉高近50%.

图1. Average bitrate for fixed quality at 1 fps using the VMAF metric

表2 shows the overall scoring for both the offline and online tests in all reported categories. Note that there are no AV1 codecs in the 30 fps category because none were able to encode at that rate.

One frustration with the report is that not all codecs are commercially available, 无论是授权还是通过本地或云编码器, which makes their inclusion largely irrelevant to report buyers looking for the best codec for their streaming operation. 例如，BVC2.0 codec is from Bytedance, the owner of TikTok and appears to be for internal use only. Same deal with the Tencent V265 which is even more confusing because the developer is listed as Tencent (a large Chinese conglomerate) while a company named Shannon Lab is marketing the Tencent Shannon Encoder (T265). It would be great if the reports designated if the codec was commercially available and provided contact 信息 for those that are.

表2. 第一部分获奖者

另一个令人沮丧的是，每个报告的编解码器都在变化. 例如, 第二部分，全高清内容，主观评价, 哪个用8个视频序列评估了11个编解码器, 不包括极光, and subjective ratings would have been valuable for any company that was considering deploying that AV1 codec. 也就是说, the work involved in gathering the subjective data is staggeringly impressive; MSU used its crowdsourced quality platform, Subjectify.us, to gather 236,736 comparisons from over 61,000 unique participants.

整体, 在1 FPS测试中, 字节跳动编解码器是其中的佼佼者, 阿里巴巴排名第二, 金山AV1编码器分列第三、四位.

图2. 主观评分1 fps编码.

表3 包含主观评分中的总获胜者, again with no AV1 codecs in the right-hand column because none could achieve 30fps encoding.

表3. 第二部分获奖者

接下来是4K和10位

第三份报告题为第三部分:4K & 10位内容，目标, compared 12 codecs using 12 UHD videos encoded at 8 and 10-bits per pixel. 在这些测试中, MainConcept HEVC编码器的表现非常好, coming in second behind BVC1 in the 8-bit encoding trials shown in 图3.

图3. 主观评分在1 fps编码

表4 显示总体结果. 请注意，只有四个编解码器参与了10位试验, 哪个MainConcept以17%的优势战胜了x265, 最接近的竞争者. If youre a premium content distributor pumping out HDR 4K streams, 这样MainConcept就会出现在你的候选列表中.

表4. 4K 8位/10位测试的总体结果

对我来说, the strongest lesson from these results is that youre going to step outside the FFmpeg box to get the best quality HEVC and AV1 encoders. 与H264, the x264 codec included in FFmpeg and most encoders based on FFmpeg was rightfully acknowledged to be best in class. HEVC和AV1的情况并非如此, where the codec in FFmpeg is outclassed by several other codecs.

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现在就订阅最新一期过去的问题

如何使用PowerShell和BASH为FFmpeg编写脚本

FFmpeg was designed as a cross-platform solution for video and audio recording, 转换, 以及使用简单的静态命令行进行流式传输. Using variables and "for loops" in a command string simplifies the reuse of existing scripts and helps automate their operation. While you can't use these scripts in the Windows Command window, you can use Microsoft PowerShell in Windows and Bash on Linux and the Mac. In this tutorial, you'll learn how to create and run such scripts with PowerShell and Bash.

2023年3月14日