Finding frame sizes in an encoded bit stream

Question

I am using HM 12.1 Reference code. I have to find frame sizes in bytes or KB from an encoded h.265 bit stream. I am very new to video processing and I am stuck in this. Pls help!

Answer 1

If you use a recent version of ffmpeg is is as simple as:

ffprobe -show_frames file.hevc

Look for lines starting with pkt_size

Example:

$ ~/src/ffmpeg/ffprobe -show_frames BQMall_832x480_60_QP22.hevc | grep pkt_size
pkt_size=67941
pkt_size=12235
pkt_size=13024
pkt_size=13026
pkt_size=12534
pkt_size=13778
pkt_size=13589
pkt_size=13039
pkt_size=12035
pkt_size=12582
pkt_size=13186
pkt_size=15519
pkt_size=15930
pkt_size=15616
pkt_size=15311
pkt_size=15430
pkt_size=14608
pkt_size=14423
pkt_size=16044
pkt_size=18246

ffprobe is pretty cool and together with gnuplot you can produce nice plots of the frame-sizes, e.g. something like this:

Currently it doesn't work for HEVC since ffprope fails to detect the correct slize-types but that will hopefully be fixed in the future

The code to do the above is:

#!/bin/bash

# If not in path
FFPROBE=/home/xxxx/src/ffmpeg/ffprobe
# If in path
#FFPROBE=ffprobe

cat <<EOF > /tmp/plot.txt
# GNUPLOT "plot.txt"
#Use the 3 lines below to store plot to file
#set terminal png size 1280,720
#set term png
#set output "bitrate.png"

set title "$(basename $1)"
set ylabel "Bytes per frame"
set xrange [-2:*]
set lmargin 12
set rmargin 2
set grid
set pointsize 2
set label 1 "I frames"
set label 1 at graph .85, .96 tc lt 1
set label 2 "P frames"
set label 2 at graph .85, .92 tc lt 2
set label 3 "B frames"
set label 3 at graph .85, .88 tc lt 3
plot '/tmp/column.dat' using 3:1:2 notitle with i lc rgb variable
EOF

awk '
BEGIN{
    FS="="
    OFS="\t"
    fnum=0
}
/pkt_size/ {size=$2}
/pict_type/{
    sub(/I/, "167116800", $2)
    sub(/P/, "65280", $2)
    sub(/B/, "255", $2)
    sub(/\?/, "65280", $2)
    type=$2
}
/coded_picture_number/{
#   sub(/0/, fnum, $2)
    num=$2
#   fnum=fnum+1
    print size, type, num
}' <(${FFPROBE} -show_frames $1 2>/dev/null) > /tmp/column.dat

gnuplot -persist /tmp/plot.txt

Update

The good guys at JCT-VC have thought about this and in the reference software, you get a binary named annexBbytecountStatic which does pretty much this. Just call it with a raw hevc-bitstream as the only argument. Using the same file as above as an example:

$ ./annexBbytecountStaticd BQMall_832x480_60_QP22.hevc | grep NumBytesInNALunit
   NumBytesInNALunit: 25
   NumBytesInNALunit: 31
   NumBytesInNALunit: 10
   NumBytesInNALunit: 67858
   NumBytesInNALunit: 12231
   NumBytesInNALunit: 13020
   NumBytesInNALunit: 13022
   NumBytesInNALunit: 12530
   NumBytesInNALunit: 13774
   NumBytesInNALunit: 13585
   NumBytesInNALunit: 13035
   NumBytesInNALunit: 12031
   NumBytesInNALunit: 12578
   NumBytesInNALunit: 13182
   NumBytesInNALunit: 15515
   NumBytesInNALunit: 15926
   NumBytesInNALunit: 15612
   NumBytesInNALunit: 15307
   NumBytesInNALunit: 15426
   NumBytesInNALunit: 14604
   NumBytesInNALunit: 14419
   NumBytesInNALunit: 16040
   NumBytesInNALunit: 18243
  NumBytesInNALunit: 338004
  NumBytesInNALunit: 270121
  NumBytesInNALunit: 0
  NumBytesInNALunit: 67883

---

Answer 2

Pay attention that:

ffprobe -show_frames file.hevc | grep pkt_size

command returns frames in display order if you need stored order use:

ffprobe -show_packets file.hevc | grep size