This will improve efficiency and accuracy of getting appropriate DRM systems when downloading segments.
This can dramatically improve download speed from less than 50 kb/s to full speed if the HLS playlist used a lot of AES-128 EXT-X-KEYs. E.g., a unique key for each segment.
This was caused because the HLS.get_drm function took EVERY EXT-X-KEY, checked for supported systems, loaded them, and returned the supported objects. This meant it could load possibly 100s of AES-128 ClearKey objects (likely requiring URL downloads for the key URI) causing a huge delay before downloading each segment.
If you use --cdm-only, you will end up licensing multiple times if the PSSH has more than one Key ID. While this is checked for, with the KID check now being more lenient, it will end up continuing and licensing again.
However, even with the original check code this would have been pointless. If the first license did not return a content key for a KID, then the next license call with the exact same parameters wouldn't have either
For ex., if a service has the same PSSH or license call for 720p and 1080p video tracks, but it doesn't return a KID for the 1080p track, then the previous code would return an error, even though it has enough content key data to continue.
With this change it now only raises the error if the track's exact KID was not licensed. This adds support to prepare_drm for specifying the track's KID.
- DASH and HSL tracks must now explicitly provide the URL to download as the init segment. This is because the original code assumed the first segment, or first init segment was the one that the caller wants, which may not be the case (e.g., and ad is the first init segment).
It now supports explicitly providing a byte-range to download, as well as modifying the fallback content size of 20KB.
It now also checks if the server supports the HTTP Range header and uses it over the hacky request-streaming method. It also checks for the file size and uses that over the fallback size as long as it's not bigger than 100 KB.
Overall it's now more dynamic to specific use-cases, and more efficient in various ways.
These only happen if we intentionally cancel the process, or failed. However, this is something that is generally obvious given the args, and when cancelling a wall of these logs would appear.
Since we now have pretty logs for them, the exception (which would be a CalledProcessError) would be generally pointless. However, the return code may be useful so that is kept.
rlaphoenix