On 2019-10-26 21:15, Michael Niedermayer wrote:
On Sat, Oct 26, 2019 at 02:05:27PM +0300, Andrey Semashev wrote:
The decoder never marks pictures as I-frames, which results in no
keyframe indication and incorrect frame skipping, in cases when
keyframes should be decoded.
This commit works around this decoder limitation and marks I-frames
and keyframes based on "freeze picture release" bit in h261 picture
header. This reflects h261enc behavior.
---
libavcodec/h261.h | 1 +
libavcodec/h261dec.c | 27 ++++++++++++++++++---------
2 files changed, 19 insertions(+), 9 deletions(-)
If the goal is correctly recognizing I frames then checking if all
blocks are intra should be the most reliable
In my case, the goal is to know when a keyframe is received, i.e. when
the receiver can be reasonably sure it can start displaying/processing
received frames. Including after some frames lost in transmission.
According to H.261 spec, "freeze picture release" bit is what is
intended to mark keyframes. To quote section 4.3.3:
<quote>
A signal from an encoder which has responded to a fast update request
and allows a decoder to exit from its freeze picture mode and display
decoded pictures in the normal manner.
</quote>
I'll reiterate that h261enc marks keyframes with this bit.
that wont work for skiping though as it requires decoding
Right.
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