I have a bunch of sound files each about an hour long, each on a particular topic, speech or a lecture. I have listened to them a few weeks ago and I would like to listen again to a section of my interest. I think I know the file but not where exactly inside the file. If I had used "chaptering" or "bookmarking" it would have been much easier and quicker.
Chapters/Bookmarks
An audio or video file could be organized in to chapters much the same like a book. It makes navigation easier. And we'd also be able to see the structure and content overview of the entire track by going through it. The basis is to include a chapter index which is a list of time pointers with titles. Many media containers support Chapter markers including MKV, WMV, DivX, MOV, OGG, AVI and MP4. Here, In this article I'm sharing my experience based on M4A, M4B and M4V file formats all based on MP4 specification.
I also happened to have photos and images relevant to the audio track. Mostly some slides relavent to sections of lectures and speeches. Wouldn't it be nice to put pictures along with the audio into one single file? It would save clutter and make reference easier. That sounds like a video with a slide show. I have only about 30 or so photos for a 1 hour long audio. Probably, a video would be less meaningful. It would take more disk space unnecessarily and a whole lot of converting and rendering times. Especially when there is a bunch to work with. Not to forget that both the audio and video quality would drop (unless we avoid lossy trancoding/reencoding somehow).
Chapter Images
Interestingly, it seems possible to directly include the images alongside sound within the audio file itself. Hopefully, we'll get them to display synchronized with audio during playback. Audio and video data streams of a file are included in what is called a container. Out of them, some formats are expected to support 'Chapter Images' which is basically an Image as a chapter marker.
This feature was promoted by Apple Inc. through the introduction of enhanced podcasts which were supposed to be better than conventional podcasts in terms of user experience. However, it remained mostly infamous, underutilized or irrelevant to the application. As a result, most media players do not know how to handle these extra still images during the playback. While Apple software like QuickTime does reasonably support the feature, it wouldn't be surprising to see it being dropped in time to come.
But nevertheless, there are commercial proprietary file formats with compatible media players that are hugely successful with this application; particularly in the Audiobook industry.
Tools and Utilities
To do these changes we require to retrieve the metadata from the multimedia file and decode it before any editing can be done sensibly. Then, we would have to encode it again and include it in the file. Let's resort to a suitable tool.
Chapter markers can be edited through many software. FFmpeg which is a powerful multimedia tool, do support read/write of metadata including chapter markers. It's a command line with a lot of other tools. If you want to stick to something simpler and easier, consider Drax, a free open source tool or MP4Box. Both allows modification of metadata and chapter markers in a MPEG-4 file. MP4Box provides a lot more control over MP4 packing.
There are only a handful of software capable of including chapter images. Subler (for Mac) and Chapter and Verse(for Windows) are a couple of freeware you can make use of.
And it seems like FFmpeg alone can be used to integrate images in the form of a slideshow with fixed or varying duration per image plus the audio.(See References for links).
Cover Art
A more common form of including images in an audio file is done in the form of cover arts or album arts. Unlike chapter images, access to these are not associated with playback time. Most metadata editors allow to add still images this way. (like MP3tag)
Conclusion
Organizing and keeping track of the content within audio and video files is difficult when you have a lot. Sectioning the track into chapters and subtitling may help with this to increase accessibility and searchability as well. However, it should be kept in mind that not all software complies in the same way. There are a variety of software with wildly implemented standards out there. You'll be fine as long as you stick with the right combination for your purpose. Particularly when it comes to the Chapter Image issue. If that is the case, a video may be the better choice.
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