hevcqp by HellGauss (HG)

---

USAGE:

1. hevcqp.exe inputFile
2. hevcqp.exe inputFile outputStatsFile

This script displays on stdout general QP statistics for hevc/h264 video in inputFile

Optionally, it writes detailed statistics for each frame in outputStatsFile

Log messages are on stderr

Requires ffmpeg.exe and ffprobe or ffprobe_mod.exe in same (current) dir or PATH

See readme for compiling ffprobe_mod.exe

Instructions for compiling ffprobe_mod are in hevcdec_mod folder.

---

Output format for general statistics (stdout):

{Frametype}: This select the group of frames considered

{N} = Number of frames in the considered group

{N/TOT} = % of N over total number frames

{Total Size} = Sum of size in bytes of frames in the considered group, as measured by ffprobe in frame->pkt_size

{Total Size/TOT} = % Total size of frame in group over total size of every frame

{Average Size} = {Total Size} / {N}

{AVERAGE QP} = Average QP of all macroblocks in the group.

{StdDev (frames)} = Standard deviation of the average QP of each frames

{StdDev (MB)} = Standard deviation of all macroblocks in all frames in the group

At the end, statistics on consecutive BFrames groups are reported.

---

Output format for per-frame statistics (outputStatsFile):

First row is number of frames. Next rows are info on each frame

{TYPE} {SIZE} {POSITION} {AVG QP} {STDEV QP-MB} {MIN-QP} {MAX-QP}

Values are separated by tab.

{TYPE} = K for keyframes. If not a key frame, as reported in pict_type by ffprobe

{SIZE} = pkt_size in FRAME field by ffprobe

{POSITION} = pkt_pos in FRAME field by ffprobe

{AVG QP} = Average QP of all macroblocks in the frame.

{STDEV QP-MB}: Standard deviation of macroBlocks QP values in the frame

{MIN-QP} {MAX-QP}: Minimum and maximum quantizer of macroblocks qp in frame.

---

TECH

• For hevc, the script launches the command

ffmpeg.exe -hide_banner -loglevel error -threads 1 -i inputFile -map 0:V:0 -c:v copy -f hevc -bsf:v hevc_mp4toannexb pipe: | ffprobe_mod.exe -threads 1 -v quiet -show_frames -show_streams -show_entries frame=key_frame,pkt_pos,pkt_size,pict_type -i pipe:

and parses stdout.

• For h264, the script launches the command

ffmpeg -hide_banner -loglevel error -threads 1 -i inputFile -map 0:V:0 -c:v copy -f h264 pipe: | ffprobe_mod -threads 1 -v quiet -show_frames -show_streams -show_entries frame=key_frame,pkt_pos,pkt_size,pict_type -debug qp -i pipe:

and parses the outputs in stdout and stderr. If ffprobe_mod is not available ffprobe is used (h264 only)

---

NOTES:

• For fast use, drag and drop video file in DragNDropHere.bat. A .txt file with general statistic and a .dat file with per frame statistic will be generated in the same dir as the input
• Progress LOG messages are reported every 200 frames analyzed
• Could not work with trimmed video, or with encoded but not presented frames. For hevc, usually the decoded frames should be +1 with respect to presented frames (see LOG messages). Last frame should not be a Bframe.
• If ffprobe_mod is not available, h264 analysis is still possible through ffprobe. hevc analysis is available only through ffprobe_mod
• For 8bit x264 encoding, QP analysis coincides with the encoding log of x264. For 10bit QP are shifted by -12.