At any given point on the y-axis, SVT-AV1 can maximize encoding speed compared with any other production encoder. For example, the M8 preset is about as efficient as libvp9 preset 0, but M8 is almost 10 times faster.
Two major open source software decoders are compatible with multiple platforms: dav1d was developed by VideoLAN and the open source community and can serve as an app-level decoder, while Google’s libgav1 is integrated into the Android SDK.
[W]e decided to integrate dav1d into the player for both iOS and Android platforms.
Segmented uploads reduce upload latency in many cases but come with a few tradeoffs. For instance, segmented uploads increase the complexity of the pipeline. There are some quality metrics that are only available per segment at transcode time, such as SSIM. These metrics are not helpful to us on a per segment basis. Therefore, we need to do a duration weighted average of the SSIM of all segments to come up with the SSIM of the whole video. Similarly, handling exceptions is more complex since there are more cases to handle.
Another performance optimization we use to improve the upload latency and save CPU utilization is something we call a “passthrough” upload. In some cases, the media that is uploaded is already ready for playback on most devices.
Vignette allows you to scan your contacts and see what it can find for free. If you wish to actually save these updates to your contact list, you must pay for a one-time in-app purchase. That purchase costs $4.99, is not a subscription, and is the only in-app purchase.
Email is used for Gravatar
Twitter
Facebook
A custom network called Instagram
另外作者有提到這個 app 不傳資料到伺服器上,都是在自己的裝置上連到上面提到的 social network 尋找:
Privacy is paramount
All the processing is done on-device; this isn’t the sort of app where your contacts are uploaded en masse to some server, and out of your control.
Apache Cassandra is a distributed database with it’s own LSM tree-based storage engine written in Java. We found that the components in the storage engine, like memtable, compaction, read/write path, etc., created a lot of objects in the Java heap and generated a lot of overhead to JVM.
然後在換完後測試可以看到效能大幅提昇,也可以看到 GC 的延遲大幅降低:
In one of our production clusters, the P99 read latency dropped from 60ms to 20ms. We also observed that the GC stalls on that cluster dropped from 2.5% to 0.3%, which was a 10X reduction!
While there might have been other Russian disinformation groups, the IRA spent $46,000 on pre-election day Facebook ads compared to $81 million spent by Clinton and Trump together, discluding political action committees who could have spent even more than that on the campaigns’ behalf.
The number of times a video is viewed on Instagram will soon no longer be a mystery.
Instagram is adding a new feature that will tally view counts much like parent company Facebook already does, eliminating a major blindspot for marketers attempting to tap into the app's 400-million strong audience organically.