admin-guide/media/visl.rst

1 .. SPDX-License-Identifier: GPL-2.0
9 This tool's objective is to help the development and testing of
10 userspace applications that use the V4L2 stateless API to decode media.
12 A userspace implementation can use visl to run a decoding loop even when
16 This driver can also trace the contents of the V4L2 controls submitted
17 to it.  It can also dump the contents of the vb2 buffers through a
25         No actual decoding of video frames is performed by visl. The
30 -----------------
32 - visl_debug: Activates debug info, printing various debug messages through
33   dprintk. Also controls whether per-frame debug info is shown. Defaults to off.
36 - visl_transtime_ms: Simulated process time in milliseconds. Slowing down the
39 - visl_dprintk_frame_start, visl_dprintk_frame_nframes: Dictates a range of
41   per-frame basis. Note that printing a lot of data can be slow through serial.
43 - keep_bitstream_buffers: Controls whether bitstream (i.e. OUTPUT) buffers are
44   kept after a decoding session. Defaults to false so as to reduce the amount of
48 - bitstream_trace_frame_start, bitstream_trace_nframes: Similar to
49   visl_dprintk_frame_start, visl_dprintk_nframes, but controls the dumping of
52 - tpg_verbose: Write extra information on each output frame to ease debugging
56 What is the default use case for this driver?
57 ---------------------------------------------
61 OUTPUT buffer data is subsequently used to debug a work-in-progress
68 their timestamps, the status of the OUTPUT and CAPTURE queues and more can be
72 ----------------
76 - FWHT
77 - MPEG2
78 - VP8
79 - VP9
80 - H.264
81 - HEVC
82 - AV1
85 -----------------
86 The trace events are defined on a per-codec basis, e.g.:
88 .. code-block:: bash
101 .. code-block:: bash
107 .. code-block:: bash
138 ------------------------------------------
142 values of bitstream_trace_frame_start and bitstream_trace_nframes. This can
148 .. code-block:: c
150 	snprintf(name, 32, "bitstream%d", run->src->sequence);
152 Dumping the values is simply a matter of reading from the file, i.e.:
156 .. code-block:: bash
170 .. code-block:: bash
185 of clutter.