On 12/4/2020 5:18 PM, Andreas Rheinhardt wrote:
James Almer:
On 12/4/2020 4:08 PM, Andreas Rheinhardt wrote:
James Almer:
On 12/4/2020 2:08 PM, Andreas Rheinhardt wrote:
James Almer:
Signed-off-by: James Almer <jamr...@gmail.com>
---
The idea of making avpriv_packet_list_* public was not liked, and
it was
suggested to just use AVFifoBuffer instead.
After this, the avpriv_packet_list_* functions can be made local to
libavformat again.
libavcodec/decode.c | 41
+++++++++++++++++++++++++++++------------
libavcodec/internal.h | 4 ++--
libavcodec/utils.c | 11 ++++++-----
3 files changed, 37 insertions(+), 19 deletions(-)
diff --git a/libavcodec/decode.c b/libavcodec/decode.c
index 5a1849f944..0550637029 100644
--- a/libavcodec/decode.c
+++ b/libavcodec/decode.c
@@ -145,22 +145,40 @@ fail2:
#define IS_EMPTY(pkt) (!(pkt)->data)
+static int copy_packet_props(void *_src, void *_dst, int size)
+{
+ AVPacket *src = _src, *dst = _dst;
+ int ret;
+
+ av_init_packet(dst);
+ ret = av_packet_copy_props(dst, src);
+ if (ret < 0)
+ return ret;> +
+ dst->size = src->size; // HACK: Needed for
ff_decode_frame_props().
+ dst->data = (void*)1; // HACK: Needed for IS_EMPTY().
+
+ return sizeof(*dst);
+}
This is not how a write function for a fifo should look like: A fifo
may
need to store the beginning of a packet at the end of the fifo and the
end of a packet at the beginning of a fifo; you can check for this by
checking whether size is < sizeof(AVPacket).
I'm already ensuring there's always sizeof(AVPacket) bytes left before
calling av_fifo_generic_write().
And? This just means one can write sizeof(AVPacket) bytes to the fifo,
not that there are sizeof(AVPacket) contiguous bytes available at the
current write pointer. The free space might be partially at the end and
partially at the beginning of the fifo buffer.
It wraps around? This is not obvious from reading the doxy.
In any case, by always incrementing the FIFO by sizeof(AVPacket) bytes
it shouldn't be an issue since it will always be a multiple of it. But
as i said, i'll just do it all outside of av_fifo_generic_write() anyway
since i can't propagate errors.
James, this is a fifo: It uses a circular buffer. Of course it wraps
around. And this is documented: "a very simple circular buffer FIFO
implementation".
Right, was thinking about it and handling it like a linked list FIFO
where you always add complete elements at the end than as a byte array
with read/write index pointers.
And as I said:
(The current implementation seems to actually only allocate
multiples of
a certain unit if all av_fifo_grow()/av_fifo_realloc2()/av_fifo_alloc()
calls use only multiples of this unit, but it doesn't seem to be
documented. Should probably be done as this simplifies using fifo
arrays.)
So, yes, it really seems to work nicely when using it to store arrays;
yet this is undocumented.
- Andreas
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