diff options
| author | Tom Rondeau <trondeau@vt.edu> | 2012-10-02 13:08:11 -0400 |
|---|---|---|
| committer | Tom Rondeau <trondeau@vt.edu> | 2012-10-03 12:26:12 -0400 |
| commit | 5fcb7ebd473709fd9e4e99d542f21d3cee5aaf05 (patch) | |
| tree | 9714995aaccdebab607c11334a16231b12a1d5d5 /docs | |
| parent | ba7a5f0721b0c0ce4e907c1137de1e82746e0223 (diff) | |
docs: Adding notes discussing how to use new max_output_buffer feature.
Also sneaking in a new analog group for gr-analog.
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/doxygen/other/group_defs.dox | 1 | ||||
| -rw-r--r-- | docs/doxygen/other/main_page.dox | 50 |
2 files changed, 51 insertions, 0 deletions
diff --git a/docs/doxygen/other/group_defs.dox b/docs/doxygen/other/group_defs.dox index 213486b7a1..4aee49ec85 100644 --- a/docs/doxygen/other/group_defs.dox +++ b/docs/doxygen/other/group_defs.dox @@ -28,6 +28,7 @@ /*! \defgroup slicedice_blk Slicing and Dicing Streams */ /*! \defgroup vocoder_blk Voice Encoders and Decoders */ /*! \defgroup digital Digital Modulation Blocks */ +/*! \defgroup analog Analog Communications Blocks */ /*! \defgroup qtgui_blk QT Graphical Interfaces */ /*! \defgroup uhd_blk UHD Interface */ /*! \defgroup audio_blk Audio Interface */ diff --git a/docs/doxygen/other/main_page.dox b/docs/doxygen/other/main_page.dox index c90ad883f6..f2ab2a4367 100644 --- a/docs/doxygen/other/main_page.dox +++ b/docs/doxygen/other/main_page.dox @@ -139,6 +139,56 @@ the FIR filter, which can receive up to 2000 items. tb.run(1000) \endcode +In some situations, you might actually want to restrict the size of +the buffer itself. This can help to prevent a buffer who is blocked +for data from just increasing the amount of items in its buffer, which +will then cause an increased latency for new samples. You can set the +size of an output buffer for each output port for every block. + +WARNING: This is an advanced feature in GNU Radio and should not be +used without a full understanding of this concept as explained below. + +To set the output buffer size of a block, you simply call: + +\code + tb.blk0.set_max_output_buffer(2000) + tb.blk1.set_max_output_buffer(2000,1) + tb.start() + print tb.blk1.max_output_buffer(0) + print tb.blk1.max_output_buffer(1) +\endcode + +In the above example, all ports of blk0 are set to a buffer size of +2000 in _items_ (not bytes), and blk1 only sets the size for output +port 1, any and all other ports use the default. The third and fourth +lines just print out the buffer sizes for ports 0 and 1 of blk1. This +is done after start() is called because the values are updated based +on what is actually allocated to the block's buffers. + +NOTES: + +1. Buffer length assignment is done once at runtime (i.e., when run() +or start() is called). So to set the max buffer lengths, the +set_max_output_buffer calls must be done before this. + +2. Once the flowgraph is started, the buffer lengths for a block are +set and cannot be dynamically changed, even during a +lock()/unlock(). If you need to change the buffer size, you will have +to delete the block and rebuild it, and therefore must disconnect and +reconnect the blocks. + +3. This can affect throughput. Large buffers are designed to improve +the efficiency and speed of the program at the expense of +latency. Limiting the size of the buffer may decrease performance. + +4. The real buffer size is actually based on a minimum granularity of +the system. Typically, this is a page size, which is typically 4096 +bytes. This means that any buffer size that is specified with this +command will get rounded up to the nearest granularity (e.g., page) +size. When calling max_output_buffer(port) after the flowgraph is +started, you will get how many items were actually allocated in the +buffer, which may be different than what was initially specified. + \section reconfigure Reconfiguring Flowgraphs |