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mmaldec: limit internal buffering

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This uses a new MMAL feature, which limits the number of extra frames
that can be buffered within the decoder. VIDEO_MAX_NUM_CALLBACKS can
be defined as positive or negative number. Positive numbers are
absolute, and can lead to deadlocks if the user underestimates the
number of required buffers. Negative numbers specify the number of extra
buffers, e.g. -1 means no extra buffer, (-1-N) means N extra buffers.

Set a gratuitous default of -11 (N=10). This is much lower than the
firmware default, which appears to be 96.

This is backwards compatible, but needs a symbol only present in newer
firmware headers. (It's an enum item, so it requires a check in
configure.)

Signed-off-by: Anton Khirnov <anton@khirnov.net>
This commit is contained in:
wm4 2016-04-14 12:21:26 +02:00 committed by Anton Khirnov
parent 45a954f5aa
commit 74beead9bd
2 changed files with 11 additions and 0 deletions
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2
configure vendored
View File

@ -1645,6 +1645,7 @@ HAVE_LIST="
libc_msvcrt
libdc1394_1
libdc1394_2
MMAL_PARAMETER_VIDEO_MAX_NUM_CALLBACKS
sdl
section_data_rel_ro
threads
@ -4628,6 +4629,7 @@ enabled mmal && { check_lib interface/mmal/mmal.h mmal_port_connect
check_lib interface/mmal/mmal.h mmal_port_connect ; }
check_lib interface/mmal/mmal.h mmal_port_connect ; } ||
die "ERROR: mmal not found"; }
enabled mmal && check_func_headers interface/mmal/mmal.h "MMAL_PARAMETER_VIDEO_MAX_NUM_CALLBACKS"
enabled omx_rpi && enable omx
enabled omx && { check_header OMX_Core.h ||
{ ! enabled cross_compile && enabled omx_rpi && {

9
libavcodec/mmaldec.c
View File

@ -67,6 +67,7 @@ typedef struct FFBufferRef {
typedef struct MMALDecodeContext {
AVClass *av_class;
int extra_buffers;
int extra_decoder_buffers;
MMAL_COMPONENT_T *decoder;
MMAL_QUEUE_T *queue_decoded_frames;
@ -380,6 +381,13 @@ static av_cold int ffmmal_init_decoder(AVCodecContext *avctx)
av_get_codec_tag_string(tmp, sizeof(tmp), format_in->encoding);
av_log(avctx, AV_LOG_DEBUG, "Using MMAL %s encoding.\n", tmp);
#if HAVE_MMAL_PARAMETER_VIDEO_MAX_NUM_CALLBACKS
if (mmal_port_parameter_set_uint32(decoder->input[0], MMAL_PARAMETER_VIDEO_MAX_NUM_CALLBACKS,
-1 - ctx->extra_decoder_buffers)) {
av_log(avctx, AV_LOG_WARNING, "Could not set input buffering limit.\n");
}
#endif
if ((status = mmal_port_format_commit(decoder->input[0])))
goto fail;
@ -796,6 +804,7 @@ AVHWAccel ff_vc1_mmal_hwaccel = {
static const AVOption options[]={
{"extra_buffers", "extra buffers", offsetof(MMALDecodeContext, extra_buffers), AV_OPT_TYPE_INT, {.i64 = 10}, 0, 256, 0},
{"extra_decoder_buffers", "extra MMAL internal buffered frames", offsetof(MMALDecodeContext, extra_decoder_buffers), AV_OPT_TYPE_INT, {.i64 = 10}, 0, 256, 0},
{NULL}
};