# Low Latency DASH - `availabilityTimeComplete=false`
Low Latency DASH manifests generated by Packager were missing the
attribute `availabilityTimeComplete`. As per the [DASH
specs](https://dashif.org/docs/CR-Low-Latency-Live-r8.pdf):
**_the AdaptationSet@availabilityTimeCompleteshould be present and be
set to 'FALSE'_**
## The Issue
The missing attribute caused ULL streams from Shaka Packager to no
longer be compatible with DASH.js. Previous versions of DASH.js allowed
users to specify ULL mode when initializing the player. However, the
most recent releases of DASH.js automatically detect ULL by scanning the
manifest for ULL specific attributes. Although there are many attributes
only associated with ULL, [DASH.js only greps for
`availabilityTimeComplete` in its detection
logic](https://github.com/Dash-Industry-Forum/dash.js/blob/development/src/streaming/controllers/PlaybackController.js#L792-L805).
Because of the missing attribute in Packager and the limited ULL
verification criteria by DASH.js, Packager streams were not being
treated as low latency streams by DASH.js.
## Testing
### Unit Testing
`./mpd_unittest
--gtest_filter="SegmentTemplateTest.OneSegmentLowLatency"`
` ./mpd_unittest
--gtest_filter="LowLatencySegmentTest.LowLatencySegmentTemplate"`
### Manual Testing
- Created a low latency stream with Shaka Packager
- Observed the expected `availabilityTimeComplete=false` attribute in
the generated DASH manifest.
It appears that not all Apple implementations follow the HLS guidelines.
While the DEFAULT=NO for an audio track should be optional and default
to NO, in practice native HLS players Safari and iOS devices treat the
missing DEFAULT as a MAYBE.
Fixes#1169
Using a rolling release of OpenSUSE was unstable. But there is another
way around the old compiler in OpenSUSE 15. This upgrades the compiler
while staying on a stable release of the OS.
A single-line change on #L170 to `wv.protection_scheme =
struct.unpack('>L', bytes(protection_scheme, encoding='utf-8'))[0]`,
needed to work around this issue on Ubuntu 22.04LTS+ running Python
3.10+:
```sh
TypeError: a bytes-like object is required, not 'str'
```
On line 170.
This issue is observed on Python 3.10+ and above.
This workaround addresses a major backwards compatibility break with a
major Python release version where collections.abc isn't available.
Fixes#1192
A single-line change on #L170 to `wv.protection_scheme =
struct.unpack('>L', bytes(protection_scheme, encoding='utf-8'))[0]`,
needed to work around this issue on Ubuntu 22.04LTS+ running Python
3.10+:
```sh
TypeError: a bytes-like object is required, not 'str'
```
On line 170.
This removes all chromium dependencies from media/base/ and completes
the build system in CMake.
The ClosureThread class and its classes were removed, as they were
specific to chromium base. ClosureThread has been replaced by
std::thread.
The byte-swapping utilities in network_util.cc have been removed and
replaced with absl.
generate_unique_temp_path() was split out of file_unittest.cc into
file_test_util.cc, where other test suites could make use of it.
WARN_UNUSED_RESULT was replaced with the C++ standard attribute
[[nodiscard]].
The base::Clock interface was replaced with a typedef for a function
pointer that returns the current time.
This re-enables the tests in http_key_fetcher_unittest.cc by using
httpbin.org.
Issue #1047 (CMake porting)
Issue #346 (absl porting)
This does not depend on absl, which frees macros.h from any library deps
that would make the CMake dependency tree more complicated. This also
fixes build errors in some environments.
mbedtls works very differently from BoringSSL, and many changes had to
be made in the details of AES decryption to accomodate this.
Beyond the basic changes required for mbedtls, part of the CTS padding
implementation had to be rewritten. I believe this is because of an
assumption that held for BoringSSL, but not for mbedtls. I was unable to
determine what it was, so I rewrote the CTS decryption using reference
materials. After this, tests passed.
The deterministc PRNG I used with mbedtls in the RSA tests differs
somewhat from the old one, so the expected vectors had to be
regenerated. The old determinstic tests were also disabled, and are now
re-enabled.
Since cryptography is sensitive code, and because there were far more
changes needed here than just updating some headers and utility function
calls, this has been split into its own PR for separate review from the
rest of the media/base porting work.
Issue #1047 (CMake porting)
Issue #346 (absl porting)
This brings some workflow improvements and fixes from the `cmake` branch
to `main`, as well as some unique fixes to keep gclient working, so that
we can continue to accept contributions in `main` until the `cmake`
merge is ready.
- Fix docs build in GitHub Actions (from `cmake` branch)
- Cancel workflow when a PR is updated (from `cmake` branch)
- Fix docker failures caused by running as root (from `cmake` branch)
- Work around exception in depot_tools on Windows
- Use Windows 2019 images in GitHub Actions for compatibility with gyp
- Remove Docker build on ArchLinux, which no longer supports python2 at
all
- (NOTE: The `cmake` branch is still building on ArchLinux. Docker
builds for Arch will be restored to the `main` branch when the `cmake`
branch is finally merged to `main`.)
This is an automated sync of common workflows for this organization.
The upstream source is:
8bfe75f0d2
Co-authored-by: Shaka Bot <shaka-bot@users.noreply.github.com>
Rewrite test_data_util.cc to locate files relative to the source file
itself, rather than using a service from chromium `base::`.
Issue #1047 (CMake porting)
Issue #346 (absl porting)
The hack of using "secrets" to store per-repo settings was not working.
The main reason is that pull_request workflows don't have access to
secrets no matter what you do. So it was impossible to make this work
for settings like "ENABLE_SELF_HOSTED" for PR tests.
This change replaces that old hack with a new one. Now a repo owner must
create a "GitHub Environment" with the name of the setting they want to
enable. Currently supported values are "self_hosted", to add self-hosted
runners to the build/test matrix, and "debug", to start an SSH server
for debugging when a workflow fails.
Issue #1047 (CMake porting)
For some reason, the status util unittest was in media/base/ instead of
status/
The broken headers in the status library were not obviously broken until
media/base/ porting started, and they were used for the first time.
Issue #1047 (CMake porting)
If another instance of the PR workflow is started for the same PR,
cancel the old one. If a PR is updated and a new test run is started,
the old test run will be cancelled automatically to conserve
resources.
Build in parallel with however many cores are available on the system.
This might not affect build times in every environment (for example, if
GitHub Actions VMs are single core).
From the initial test run of this PR, we're seeing roughly 1x build
speed on Linux, 3x on macOS, and 1.5x on Windows, compared to the same
build step on a contemporaneous PR.
The docs build in GitHub Actions broke with the release of jinja 3.1,
which introduced a breaking change that broke the cloud_sptheme sphinx
extension in use by our docs. That extension is not maintained any more,
so there will be no upstream fix. See also
https://foss.heptapod.net/doc-utils/cloud_sptheme/-/issues/47
That extension adds support for table styling (see
https://cloud-sptheme.readthedocs.io/en/latest/lib/cloud_sptheme.ext.table_styling.html),
but we only appear to have one table in the docs currently
(docs/source/options/segment_template_formatting.rst) and it does not
use the options added by the cloud_sptheme extension.
Therefore the best fix for GitHub Actions and any other system running
jinja 3.1 is to remove that extension from our config.
Note:
* An xHE-AAC capable encoder will auto adjust the user-specified SAP/RAP
value to the allowed grid where SAP/RAPs can occur.
e.g.: `-rapInterval 5000` (5s) may result in actual SAPs/RAPs every
4.984s.
* To ensure SAP/RAP starts a new segment, Shaka needs to executed with a
"--segment_duration" is less than or equal to that adjusted value.
* If every SAP/RAP should trigger a new segment, just set the segment
length to a very low value e.g.: `--segment_duration 0.1`
Note:
* An xHE-AAC capable encoder will auto adjust the user-specified SAP/RAP
value to the allowed grid where SAP/RAPs can occur.
e.g.: `-rapInterval 5000` (5s) may result in actual SAPs/RAPs every
4.984s.
* To ensure SAP/RAP starts a new segment, Shaka needs to executed with a
"--segment_duration" is less than or equal to that adjusted value.
* If every SAP/RAP should trigger a new segment, just set the segment
length to a very low value e.g.: `--segment_duration 0.1`
This also normalizes the structure of all submodule folders so that
there is a clear place to put configurations, outside the submodule
source, but limited in scope to that folder.
Issue #1047 (New build system)
This removes apple_apsl and libevent (which are no longer used) and
libxml and protobuf (which will be replaced in a follow-up with
submodules).
This change only contains deletions, to make it easier to review
separately from later additions for submodules and cmake integration.
Issue #1047 (New build system)
There are a lot of changes in this first phase, because there was a
lot of infrastructure required to get some meaningful amount of
porting done. Future PRs should be simpler.
<b>Summary of changes:</b><details>
- Remove old deps:
- boringssl (replaced with mbedtls, lighter, easier to build)
- gflags (replaced with absl::flags)
- Chromium build tools
- New deps to replace parts of Chromium base:
- abseil-cpp
- glog
- nlohmann::json (for tests only)
- Submodules, updates, and CMake build rules for third-party
libraries:
- curl
- gmock/gtest
- Ported internal libraries and their tests by removing Chromium deps
and adding CMake build rules:
- file (now using C++17 filesystem APIs)
- license_notice
- status
- version
- Test improvements
- Removed file tests that can never be re-enabled
- Re-enabled all other disabled file tests
- Debug JSON values when HTTP tests fail
- Fixed chunked-encoding issues in HTTP tests
- Updated and refactored Dockerfiles testing
- All docker files working, with OS versions updated to meet the
new tool requirements
- Local docker builds no longer write files to your working
directory as root
- Local docker builds can now be run in parallel without clobbering
each others' build outputs
- DEBUG=1 can drop you into an interactive shell when a docker
build fails
- Updated and heavily refactored workflows and Dockerfiles
- All docker files now tested in parallel on GitHub, speeding up CI
- All common workflow components broken out and using workflow_call
instead of custom actions
- Self-hosted runners now optional, to make testing easier on forks
- CMake porting works-in-process can now be fully tested on GitHub
- Building ported libraries and passing ported tests on all three
platforms!
- CI hacks for macOS removed, now testing on macos-latest!
- Python2 no longer required! (Only Python3)
- Using strict build flags, treating all warnings as errors.
</details>
<b>Required to build:</b>
- CMake >= 3.16
- Python 3
- A compiler supporting C++ >= 17
- g++ >= 9 if using GCC (Clang also fine)
- MSVC for Windows
<b>Still needs work:</b><details>
- Moving other dependencies into submodules (if we keep them):
- apple_apsl
- icu
- libevent
- libpng
- libwebm
- libxml
- modp_b64
- protobuf
- zlib
- Port remaining internal libraries:
- app
- hls
- media/base
- media/chunking
- media/codecs
- media/crypto
- media/demuxer
- media/event
- media/formats/dvb
- media/formats/mp2t
- media/formats/mp4
- media/formats/packed_audio
- media/formats/ttml
- media/formats/webm
- media/formats/webvtt
- media/formats/wvm
- media/origin
- media/public
- media/replicator
- media/trick_play
- mpd
- Port main application
- Add logging flags in absl and connect them to glog (which expects
gflags)
- Port pssh-box.py
- Port main test targets (packager_test.py and packager_app.py)
- Updating all requirement and build documentation
- Remove any remaining refs to gclient, depot_tools, ninja
- Update and complete release workflows using release-please
</details>
Issue #346 (Switch to abseil)
Issue #1047 (New build system)
Caitlin O'Callaghan
Dennis E. Mungai
Marcus Spangenberg
Mark Sargent
Joey Parrish
Bartek Zdanowski
Joey Parrish
Carlos Bentzen
Shaka Bot
Geoff Jukes