media: bcm2835-codec: Limit video callbacks #4646
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Limit the number of allowed video callbacks. This helps with limiting the size of the coded input FIFO which in turn helps to control latency. Choose -5 as the magic number as it translates to DPB+5 buffers which has been proven to be a good number in the past. Ideally coded buffers would not be returned to the user until they had been decoded into the DPB or been discarded as bad, but that grade of control is unavailable to us. Signed-off-by: John Cox <jc@kynesim.co.uk>
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The helps with (but on its own does not solve) some of my issues with ffmpeg on the command line + hwaccel. As stated above I picked -5 as its a number Dom has used in the past that seemed to work. Ideally -1 or -2 would be better but those have stalled for Dom in the past so don't do that. |
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I used this setting for kodi with mmal acceleration as otherwise the latency between enqueued and dequeued buffers can grow to several seconds and media players generally don't expect that behaviour. |
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I see no issues with that, although it'd be useful to check it against GStreamer. Give me a mo to do that. |
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All good in GStreamer (1.18.4 anyway), so I'm good with it. |
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kernel: ARM: dts: vc4-kms-v3d: Always disable firmware HDMI See: raspberrypi/linux#4652 kernel: media: bcm2835-codec: Limit video callbacks See: raspberrypi/linux#4646 kernel: staging/bcm2835-camera: Add support for H264_MIN_QP, H264_MAX_QP, MPEG_VIDEO_FORCE_KEY_FRAME See: raspberrypi/linux#4647 kernel: bcm2835-isp: Colorspace fixes See: raspberrypi/linux#4643 kernel: Unicam Media Controller support See: raspberrypi/linux#4641 kernel: config: Enable FSFS_FS_SECURITY See: raspberrypi/linux#4637 kernel: gpio: bcm-virt: Fix the get() method See: raspberrypi/linux#4638 firmware: userland: Reduce debug_sym error messages See: https://forums.raspberrypi.com/viewtopic.php?f=98&t=322238 firmware: arm_dt: Increase maximum line length to 98 See: raspberrypi/linux#4638
popcornmix
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kernel: ARM: dts: vc4-kms-v3d: Always disable firmware HDMI See: raspberrypi/linux#4652 kernel: media: bcm2835-codec: Limit video callbacks See: raspberrypi/linux#4646 kernel: staging/bcm2835-camera: Add support for H264_MIN_QP, H264_MAX_QP, MPEG_VIDEO_FORCE_KEY_FRAME See: raspberrypi/linux#4647 kernel: bcm2835-isp: Colorspace fixes See: raspberrypi/linux#4643 kernel: Unicam Media Controller support See: raspberrypi/linux#4641 kernel: config: Enable FSFS_FS_SECURITY See: raspberrypi/linux#4637 kernel: gpio: bcm-virt: Fix the get() method See: raspberrypi/linux#4638 firmware: userland: Reduce debug_sym error messages See: https://forums.raspberrypi.com/viewtopic.php?f=98&t=322238 firmware: arm_dt: Increase maximum line length to 98 See: raspberrypi/linux#4638
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Limit the number of allowed video callbacks. This helps with limiting
the size of the coded input FIFO which in turn helps to control latency.
Choose -5 as the magic number as it translates to DPB+5 buffers which
has been proven to be a good number in the past.
Ideally coded buffers would not be returned to the user until they
had been decoded into the DPB or been discarded as bad, but that grade
of control is unavailable to us.
Signed-off-by: John Cox jc@kynesim.co.uk