From 8ce409aacf1be223c567fbe9c8c4e51cd7511e78 Mon Sep 17 00:00:00 2001
From: Jonas Smedegaard <dr@jones.dk>
Date: Tue, 9 Feb 2021 22:27:56 +0100
Subject: tidy: update TODOs

---
 localvideowebencode | 94 ++++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 64 insertions(+), 30 deletions(-)

diff --git a/localvideowebencode b/localvideowebencode
index 624e895..75dfcdb 100755
--- a/localvideowebencode
+++ b/localvideowebencode
@@ -19,36 +19,70 @@
 # Recommends: moreutils vainfo vpx-tools vorbis-tools opus-tools
 #
 # TODO:
-#  * Offer to skip rendering again if an output file exist already.
-#  * Support --width and --height, resolving the other part from input
-#    or forced aspect ratio.
-#  * Check and fail if all needed tools are not available.
-#  * Test if beneficial to apply real_time=-2.
-#  * Normalize each infile separately when xml fed as infile keeps sync.
-#    Maybe as workaround re-feed audio separately from xml, as done at
-#    <http://bernaerts.dyndns.org/linux/74-ubuntu/214-ubuntu-stabilize-video-melt>.
-#  * Resolve flash player to use.
-#  * Make choice of encoders configurable.
-#  * Figure out how to apply application option when using opusenc.
-#  * Handle channels per-codec for low-bitrate joint stereo Opus speech.
-#  * Double-check audio bandwidth algorithms:
-#    http://trac.ffmpeg.org/wiki/Encode/HighQualityAudio
-#  * Change VP8/VP9 bandwidth algorithm:
-#    Use https://developers.google.com/media/vp9/settings/vod/
-#  * Tune VP8 parameters:
-#    http://www.webmproject.org/docs/encoder-parameters/
-#  * Tune VP9 parameters:
-#    https://sites.google.com/a/webmproject.org/wiki/ffmpeg/vp9-encoding-guide
-#  * Support DASH:
-#    https://sites.google.com/a/webmproject.org/wiki/adaptive-streaming/instructions-to-playback-adaptive-webm-using-dash
-#  * Support watermark
-#  * Support live streaming - i.e. from (maybe faked) endless source
-#    + Lipsync may require single stream of equally chunked tracks:
-#      https://sites.google.com/a/webmproject.org/wiki/adaptive-streaming/instructions-to-do-webm-live-streaming-via-dash
-#  * Support realtime streaming - i.e. with less than 200ms latency
-#  * Compute (or hardcode) html5 codec types:
-#    + Use mp4v2-utils
-#    + http://stackoverflow.com/a/16365526
+#  * improve workflow
+#    + check initially and fail if all needed tools are not available
+#    + offer to skip rendering again if an output file exist already
+#    + maybe support extracting keyframes to aid in picking cover image
+#      <https://video.stackexchange.com/questions/26066/dump-keyframes-of-a-livestream>
+#      <https://video.stackexchange.com/questions/21970/speed-up-a-video-30x-using-only-key-frames-with-ffmpeg>
+#    + offer to produce a full ladder at once
+#      <https://developers.google.com/media/vp9/settings/vod>
+#      <https://developer.apple.com/documentation/http_live_streaming/hls_authoring_specification_for_apple_devices>
+#  * improve configurability
+#    + support --width and --height,
+#      resolving other dimension from (explicit or source) aspect ratio
+#    + make choice of encoders configurable
+#  * tune defaults
+#    + adapt VP8/VP9 quantizer based on frame size
+#      <https://developers.google.com/media/vp9/settings/vod#quality>
+#    + maybe pass option real_time=-2 to melt
+#      <https://www.reddit.com/r/kdenlive/comments/ka0aak/kdenlive_gpucpu_use_threads_mlt_and_ffmpeg_tips/>
+#    + maybe reduce threads to "spend" total available cores only once
+#    + apply application option when using opusenc
+#    + use joint stereo for low-bitrate Opus speech
+#    + maybe refine audio bandwidth algorithms
+#      <http://trac.ffmpeg.org/wiki/Encode/HighQualityAudio>
+#    + change VP8/VP9 bandwidth algorithm
+#      <https://developers.google.com/media/vp9/settings/vod/>
+#    + tune VP8 parameters:
+#      <http://www.webmproject.org/docs/encoder-parameters/
+#    + tune VP9 parameters
+#      <https://sites.google.com/a/webmproject.org/wiki/ffmpeg/vp9-encoding-guide>
+#    + compute (or hardcode) html5 codec types, e.g. using mp4v2-utils
+#      <http://stackoverflow.com/a/16365526>
+#    + generalize GOP handling, with keyframes every ~8s by default
+#      which fits 48kHz audio at 25 fps (200f) and 30fps (240f),
+#      or an "LL" option of 48f (1.92s at 25fps or 1.6s at 30fps)
+#    + generalize GOP handling,
+#      with default "normal" option of 200f@25fps or 240f@30fps (both 8s)
+#      and "low-latency" option of 48f (1.92s at 25fps or 1.6s at 30fps)
+#      <https://stackoverflow.com/questions/30979714/how-to-change-keyframe-interval-in-ffmpeg/41735741#41735741>
+#      <http://anton.lindstrom.io/gop-size-calculator/>
+#      <https://docs.unified-streaming.com/best-practice/content-preparation.html#recommended-fragment-boundaries-are-aligned-across-all-tracks-audio-video-text>
+#  * players
+#    + disable flash player by default
+#    + support HLS player, when HLS is supported
+#      <https://github.com/video-dev/hls.js>
+#  * normalize each infile separately when xml fed as infile keeps sync
+#    maybe as workaround re-feed audio separately from xml, as done at
+#    <http://bernaerts.dyndns.org/linux/74-ubuntu/214-ubuntu-stabilize-video-melt>
+#  * support DASH
+#    <https://sites.google.com/a/webmproject.org/wiki/adaptive-streaming/instructions-to-playback-adaptive-webm-using-dash>
+#  * support watermark
+#  * support superstable live streaming, e.g. (maybe faked) endless source
+#    + lipsync may require single stream of equally chunked tracks
+#      <https://sites.google.com/a/webmproject.org/wiki/adaptive-streaming/instructions-to-do-webm-live-streaming-via-dash>
+#  * support adaptive streaming
+#    + compute ladder from mathematical model
+#      as in "Optimal design of encoding profiles for ABR streaming"
+#      <http://www.reznik.org/publications.html>
+#  * support low-latency streaming a.k.a. "LL", i.e. 3-5s latency
+#    + LL-HLS
+#      <https://stackoverflow.com/questions/56700705/how-to-enable-lhls-in-ffmpeg-4-1>
+#    + CMAF, using either fmpeg or (when released) GPAC
+#      <https://github.com/FFmpeg/FFmpeg/commit/cc929ce>
+#      <https://github.com/gpac/gpac/commit/4529c60>
+#  * support realtime streaming a.k.a. "ULL", i.e. less than 0.5s latency
 
 set -e
 
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