( Alucard | 2022. 02. 21., h – 10:12 )

Szerintem a GStreamer-ben lesz a probléma.

Itt egy érdekes rész a doksiból:

https://gstreamer.freedesktop.org/documentation/application-development/advanced/buffering.html?gi-language=c#stream-buffering

In this case we are reading from a slow network source into a buffer element (such as queue2).

The buffer element has a low and high watermark expressed in bytes. The buffer uses the watermarks as follows:

  • The buffer element will post BUFFERING messages until the high watermark is hit. This instructs the application to keep the pipeline PAUSED, which will eventually block the srcpad from pushing while data is prerolled in the sinks.

  • When the high watermark is hit, a BUFFERING message with 100% will be posted, which instructs the application to continue playback.

  • When during playback, the low watermark is hit, the queue will start posting BUFFERING messages again, making the application PAUSE the pipeline again until the high watermark is hit again. This is called the rebuffering stage.

  • During playback, the queue level will fluctuate between the high and the low watermark as a way to compensate for network irregularities.

This buffering method is usable when the demuxer operates in push mode. Seeking in the stream requires the seek to happen in the network source. It is mostly desirable when the total duration of the file is not known, such as in live streaming or when efficient seeking is not possible/required.

The problem is configuring a good low and high watermark. Here are some ideas:

  • It is possible to measure the network bandwidth and configure the low/high watermarks in such a way that buffering takes a fixed amount of time.

    The queue2 element in GStreamer core has the max-size-time property that, together with the use-rate-estimate property, does exactly that. Also the playbin buffer-duration property uses the rate estimate to scale the amount of data that is buffered.

  • Based on the codec bitrate, it is also possible to set the watermarks in such a way that a fixed amount of data is buffered before playback starts. Normally, the buffering element doesn't know about the bitrate of the stream but it can get this with a query.

  • Start with a fixed amount of bytes, measure the time between rebuffering and increase the queue size until the time between rebuffering is within the application's chosen limits.

The buffering element can be inserted anywhere in the pipeline. You could, for example, insert the buffering element before a decoder. This would make it possible to set the low/high watermarks based on time.

The buffering flag on playbin, performs buffering on the parsed data. Another advantage of doing the buffering at a later stage is that you can let the demuxer operate in pull mode. When reading data from a slow network drive (with filesrc) this can be an interesting way to buffer.

Ebből arra következtetek, hogy arch-ék máshogyan lövik be default a low/high watermark értékeket, ezért akad a lejátszás. Viszont jó hír, hogy a Strawberry lehetőséget kínál mindkét érték módosítására, szóval elvileg kikísérletezhető a megfelelő beállítás.