[BUG]Silence At The Beginning Of Playback/capture With IPC4
Introduction
In this article, we will discuss a bug that causes silence at the beginning of playback/capture with IPC4. This issue is observed when using the aplay command to play a file, and it is exacerbated by increased DAI DMA buffer sizing. We will delve into the root cause of this problem, provide steps to reproduce it, and discuss the expected behavior and impact of this bug.
Describe the Bug
The bug in question causes a minimum of 4 periods of silence at the beginning of playback/capture with IPC4. This silence increases with increased DAI DMA buffer sizing. The root cause of this issue lies in the way the sink pipelines are triggered, which results in the link DMA being activated before the first data is available. As a result, the first data comes out after the read pointer wraps around the entire buffer, which is a minimum of 4 periods long.
Impact of DAI DMA Buffer Sizing
The size of the DAI DMA buffer has a direct impact on the amount of silence observed at the beginning of playback/capture. As the buffer size increases, so does the amount of silence. This is because the larger buffer size allows for more data to be stored before the read pointer wraps around, resulting in a longer period of silence.
Expected Behavior
The expected behavior in this scenario is for there to be no silence at the beginning of playback/capture, or at the very least, minimal silence. However, due to the bug, a significant amount of silence is observed, which can be detrimental to the overall audio experience.
Reproduction Rate
The reproduction rate of this bug is 100%, meaning that it can be consistently reproduced using the aplay command with the specified parameters.
Environment
The bug was observed on the following platforms and with the following configurations:
- Kernel: topic/sof-dev
- SOF: main
- Topology file: sof-ptl-nocodec.tplg
- Platform: PTL
Steps to Reproduce
To reproduce this bug, follow these steps:
- Install the necessary packages: Install the necessary packages, including the aplay command, on your system.
- Create a test file: Create a test file, such as a WAV file, to use for playback.
- Run the aplay command: Run the aplay command with the following parameters:
aplay -D:hw0,0 file.wav - Observe the output: Observe the output of the aplay command and note the presence of silence at the beginning of playback.
Conclusion
In conclusion, the bug causing silence at the beginning of playback/capture with IPC4 is a significant issue that affects the overall audio experience. The root cause of this problem lies in the way the sink pipelines are triggered, resulting in the link DMA being activated before the first data is available. By understanding the impact of DAI DMA buffer sizing and the expected behavior, we can work towards resolving this bug and providing a better audio experience for users.
Additional Information
The following screenshot illustrates the issue:
As shown in the screenshot, the top waveform represents the output with a DMA buffer size of 16 periods, the second waveform represents the output with a DMA buffer size of 8 periods, and the third waveform represents the default output with a DMA buffer size of 4 periods. The silence at the beginning of playback is evident in all three waveforms, with the amount of silence increasing with increased DMA buffer sizing.
Future Work
Introduction
In our previous article, we discussed a bug that causes silence at the beginning of playback/capture with IPC4. This issue is observed when using the aplay command to play a file, and it is exacerbated by increased DAI DMA buffer sizing. In this article, we will answer some frequently asked questions about this bug and provide additional information to help resolve the issue.
Q: What is the root cause of this bug?
A: The root cause of this bug lies in the way the sink pipelines are triggered, resulting in the link DMA being activated before the first data is available. This causes the read pointer to wrap around the entire buffer, resulting in a minimum of 4 periods of silence at the beginning of playback/capture.
Q: How does DAI DMA buffer sizing affect the amount of silence?
A: The size of the DAI DMA buffer has a direct impact on the amount of silence observed at the beginning of playback/capture. As the buffer size increases, so does the amount of silence. This is because the larger buffer size allows for more data to be stored before the read pointer wraps around, resulting in a longer period of silence.
Q: What is the expected behavior in this scenario?
A: The expected behavior in this scenario is for there to be no silence at the beginning of playback/capture, or at the very least, minimal silence. However, due to the bug, a significant amount of silence is observed, which can be detrimental to the overall audio experience.
Q: How can I reproduce this bug?
A: To reproduce this bug, follow these steps:
- Install the necessary packages: Install the necessary packages, including the aplay command, on your system.
- Create a test file: Create a test file, such as a WAV file, to use for playback.
- Run the aplay command: Run the aplay command with the following parameters:
aplay -D:hw0,0 file.wav - Observe the output: Observe the output of the aplay command and note the presence of silence at the beginning of playback.
Q: What are the system requirements for this bug?
A: The bug was observed on the following platforms and with the following configurations:
- Kernel: topic/sof-dev
- SOF: main
- Topology file: sof-ptl-nocodec.tplg
- Platform: PTL
Q: How can I resolve this bug?
A: To resolve this bug, we need to investigate further and identify the root cause of the issue. This may involve modifying the sink pipelines to trigger the link DMA only after the first data is available, or adjusting the DAI DMA buffer sizing to minimize the amount of silence observed. By working together, we can provide a better audio experience for users and resolve this bug once and for all.
Q: What are the potential consequences of not resolving this bug?
A: If this bug is not resolved, it can lead to a poor audio experience for users, with significant amounts of silence at the beginning of playback/capture. This can be detrimental to the overall user experience and may lead to user frustration and dissatisfaction.
Conclusion
In conclusion, the bug causing silence at the beginning of playback/capture with IPC4 is a significant issue that affects the overall audio experience. By understanding the root cause of the issue, the impact of DAI DMA buffer sizing, and the expected behavior, we can work towards resolving this bug and providing a better audio experience for users.