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fix: sample video quality #761

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Merged
ptpt merged 5 commits into from
Jun 24, 2025
Merged

fix: sample video quality #761

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f6a2a6a
fix: sample video quality
ptpt Jun 24, 2025
bd8070a
add comment
ptpt Jun 24, 2025
d2a3c4b
fix typo
ptpt Jun 24, 2025
9c595ec
generate_binary_search
ptpt Jun 24, 2025
6083f62
Revert "generate_binary_search"
ptpt Jun 24, 2025
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24 changes: 10 additions & 14 deletions mapillary_tools/ffmpeg.py
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Original file line number Diff line number Diff line change
Expand Up @@ -169,12 +169,10 @@ def extract_frames(
sample_prefix = sample_dir.joinpath(video_path.stem)
if stream_idx is not None:
stream_selector = ["-map", f"0:{stream_idx}"]
ouput_template = f"{sample_prefix}_{stream_idx}_%06d{FRAME_EXT}"
stream_specifier = f"{stream_idx}"
output_template = f"{sample_prefix}_{stream_idx}_%06d{FRAME_EXT}"
else:
stream_selector = []
ouput_template = f"{sample_prefix}_{NA_STREAM_IDX}_%06d{FRAME_EXT}"
stream_specifier = "v"
output_template = f"{sample_prefix}_{NA_STREAM_IDX}_%06d{FRAME_EXT}"

cmd: list[str] = [
# global options should be specified first
Expand All @@ -186,12 +184,12 @@ def extract_frames(
# filter videos
*["-vf", f"fps=1/{sample_interval}"],
# video quality level (or the alias -q:v)
*[f"-qscale:{stream_specifier}", "2"],
*["-qscale:v", "2"],
# -q:v=1 is the best quality but larger image sizes
# see https://stackoverflow.com/a/10234065
# *["-qscale:v", "1", "-qmin", "1"],
# output
ouput_template,
output_template,
]

self._run_ffmpeg(cmd)
Expand Down Expand Up @@ -227,12 +225,10 @@ def extract_specified_frames(
sample_prefix = sample_dir.joinpath(video_path.stem)
if stream_idx is not None:
stream_selector = ["-map", f"0:{stream_idx}"]
ouput_template = f"{sample_prefix}_{stream_idx}_%06d{FRAME_EXT}"
stream_specifier = f"{stream_idx}"
output_template = f"{sample_prefix}_{stream_idx}_%06d{FRAME_EXT}"
else:
stream_selector = []
ouput_template = f"{sample_prefix}_{NA_STREAM_IDX}_%06d{FRAME_EXT}"
stream_specifier = "v"
output_template = f"{sample_prefix}_{NA_STREAM_IDX}_%06d{FRAME_EXT}"

# Write the select filter to a temp file because:
# The select filter could be large and
Expand Down Expand Up @@ -269,8 +265,8 @@ def extract_specified_frames(
# vsync is deprecated by fps_mode,
# but fps_mode is not avaliable on some older versions ;(
# *[f"-fps_mode:{stream_specifier}", "passthrough"],
# Set the number of video frames to output
*[f"-frames:{stream_specifier}", str(len(frame_indices))],
# Set the number of video frames to output (this is an optimization to let ffmpeg stop early)
*["-frames:v", str(len(frame_indices))],
# Disabled because it doesn't always name the sample images as expected
# For example "select(n\,1)" we expected the first sample to be IMG_001.JPG
# but it could be IMG_005.JPG
Expand All @@ -279,12 +275,12 @@ def extract_specified_frames(
# *["-frame_pts", "1"],
],
# video quality level (or the alias -q:v)
*[f"-qscale:{stream_specifier}", "2"],
*["-qscale:v", "2"],
# -q:v=1 is the best quality but larger image sizes
# see https://stackoverflow.com/a/10234065
# *["-qscale:v", "1", "-qmin", "1"],
# output
ouput_template,
output_template,
]
self._run_ffmpeg(cmd)
finally:
Expand Down