Slim::Player::Pipeline is used for transcoding. It appears, from inspection of the code, that it may return a premature end-of-file to its consumer. If the processes in the pipeline are still processing data, but it is not yet available to be read by the consumer, then end-of-file on the source will be returned as such to the consumer, thereby discarding the in-processing data.

Also the pipeline input pipe is not closed upon source end-of-file. It might be that the transcoding processes require an end-of-file marker to properly flush the data through the pipeline.