Support for audio overlays with Read Aloud?

[msypkenssmit]

According to this article EPUB3 audio overlays should be supported in the latest Calibre:
https://www.omgubuntu.co.uk/2023/12/...dio-epub-notes
I cannot find it confirmed so clearly on Calibre's website though. Is it supported?

I could not get it to work yet, but everything suggests that it should work. The only thing not working is the audio coming through.

I have tried it with this Audio-ebook here:
https://www.readbeyond.it/ebooks/b7b497df.html
See attached picture: a bar appears, Calibre is highlighting the sentences, but I hear no sound.
With another Audio-ebook I get the same.

When I try Read Aloud with a regular ebook, without embedded audio, then I do hear audio. See the other attached screenshot. Now the bar appears at the right top instead of the bottom center. It has an extra icon to configure the voices.

So:
1) Are EPUB3 audio-ebooks supposed to work?
2) If yes, how do I get audio? What can I try to debug the issue?
I have already run with 'calibre-debug -w <bookname>.epub' but there are no prints related to audio:

QPA platform: xcb
devicePixelRatio: 1.0
logicalDpi: 96.0 x 96.0
physicalDpi: 81.55183946488295 x 81.64285714285714
ApplicationPaletteChange event ignored
Using calibre Qt style: True
Path override failed for key base::DIR_APP_DICTIONARIES and path '/home/matthijs/calibre-bin/calibre/bin/qtwebengine_dictionaries'
Path override failed for key base::DIR_APP_DICTIONARIES and path '/home/matthijs/calibre-bin/calibre/libexec/qtwebengine_dictionaries'
Path override failed for key base::DIR_APP_DICTIONARIES and path '/home/matthijs/calibre-bin/calibre/libexec/qtwebengine_dictionaries'
[0.000] Load of book started
[0.002] prepared emitted
[0.040] webview loading requested
[0.186] bridge ready
[0.317] iframe ready
[0.417] loading finished
Path override failed for key base::DIR_APP_DICTIONARIES and path '/home/matthijs/calibre-bin/calibre/libexec/qtwebengine_dictionaries'

[kovidgoyal]

next release

[msypkenssmit]

♥️ looking forward to testing it!

[kovidgoyal]

Well actually, now that I think about it, the next release is basically adding support for the audio/mpeg format to the calibre viewer. MP3 should work already and does for me, which is what the audio ebook sfrom read beyond use. The symptom you describe of audio not playing is something else, probably related to some incompatibility on Linux or the other. Use the official calibre binaries and see if it works.

[msypkenssmit]

That's a pity!

I'm currently running the latest binaries from the website, installed for the local user with

wget -nv -O- https://download.calibre-ebook.com/linux-installer.sh | sh /dev/stdin install_dir=~/calibre-bin isolated=y

I'm running Debian bookworm, but I don't have Debian's build of Calibre installed, instead I only have the binaries from the website.

As I have mentioned before, I do hear audio for the TTS Read Aloud, so audio is partially working. Just not when it should be playing back the embedded audio files.

I'm willing to go to considerable lengths to investigate, when provided with some instructions.

[kovidgoyal]

TTS read aloud goes via QtMultimedia playing mp3 files in the viewer goes via QtWebEngine. As far as I know they both use ffmpeg under the hood so I have no idea why one would work for you and the other wouldnt. You should be able to workaround it by using the calibre content server and viewing the book in a browser instead, assuming audio is working in your browser.

[msypkenssmit]

I just tried yesterday's release 7.21.0, and now it works! So, whatever you did, it may have made the difference for me.
For good measure I tried to play audio from the browser first and simultaneously, but even that did not break the playback again. Hopefully it will stay that way.

One thing I did notice is that the highlight for Read Aloud when the audio is coming from the book itself is not following the highlight color from the book.

In the .opf there is a line like this

<meta property="media:active-class">-epub-media-overlay-active</meta>

Which indicates that in the .css the following attribute can be used to indicate the highlight color.

/* Media Overlay highlight color: yellow */
.-epub-media-overlay-active {
    background-color: #FFFF00;
}

Is this something that on Calibre's road map to support?

If not (soon), is there a way to configure the highlight color for Read Aloud through custom styling?

[kovidgoyal]

Its a simple selection, you can style the selection color using standard CSS.

[Comfy.n]

I'm using this on Viewer custom CSS:

PHP Code:

::selection {background: yellow; color:#000;} 


[thiago.eec]

Originally Posted by Comfy.n

I'm using this on Viewer custom CSS:

PHP Code:

::selection {background: yellow; color:#000;} 


Nice tip!