[mythtv-users] AudioOutputGraph progress

Mark Kendall mark.kendall at gmail.com
Fri Feb 12 09:45:06 UTC 2021

On Thu, 11 Feb 2021 at 16:54, John Pilkington <johnpilk222 at gmail.com> wrote:
> Hi Mark :  Thanks for looking at this (among much else).  I have b15f981
> running in F32 and have looked at a recorded GTS (Greenwich Time Signal)
> on BBC Radio 4.  A good AOG could be helpful for editing radio, while
> for video the picture provides the most important editing clues.
> In radio the positioning isn't accurate or repeatable - and the display
> timescale varies too.  My recording began 2 minutes early, and the
> 'imaginary' video frame rate is 25 fps.  Hence the start of the final
> pip should be at 3000 frames, and the start of the first at 2875.
> Stopping playback at the first audible pip shows a frame count around
> 2810, while the first to show in the AOG has been around 2720 and the
> last around 2830.  In the past, only step sizes in radio down to 1
> second have worked reasonably well.
> I tried making improvements in this some time ago, but my efforts seemed
> more likely to break things than yield improvements.  I hope and expect
> that you can do better :-)

Hi John,

The only functional changes I've made to the audiograph code to date
were to fix the crash on macos. The subsequent changes were purely

In testing those changes, I pretty much decided that the cutlist
editor is a bit of a mess at the moment. Using VAAPI for decoding,
seeking was erratic in a number of ways and as such, if I were using
the editor, I wouldn't be comfortable that the frame displayed is the
correct one (note: software decoding is much better - though I
wouldn't describe it as perfect). Likewise, although I can't be sure,
it really doesn't look like the audio graph is showing consistently
accurate data. I've never really used that functionality and so don't
know whether it is a regression or not. I'm a little more familiar
with the code now.

Going forward, the player code is only part way through a sizeable
re-factoring - and one of the aims is to significantly improve
handling of audio only streams. So I'm hoping that much of the audio
only/radio stream issues will start to resolve themselves. Likewise,
once the current round of changes is done, I'll start looking at the
decoder in a little more detail - which hopefully will start to
resolve some of the minor seek issues.

All told - what I'm trying to say is - stick with it, there is a plan
and I'm hoping it will all come together before 0.32 is released.

Thanks and regards

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