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Transcoding av1 by cpu debugging #518

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Merged
ShaneIsrael merged 2 commits into from
Mar 26, 2026
Merged

Transcoding av1 by cpu debugging #518

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df7eefb
use temporary file, drain stderr in background thread and log to console
ShaneIsrael Mar 24, 2026
13c75a7
fix file tmp file naming issue
ShaneIsrael Mar 25, 2026
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11 changes: 11 additions & 0 deletions app/server/fireshare/cli.py
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Original file line number Diff line number Diff line change
Expand Up @@ -787,6 +787,17 @@ def handle_cancel(signum, frame):
# Write initial transcoding status with our PID so the API can track us
util.write_transcoding_status(paths['data'], 0, total_jobs, pid=os.getpid())

# Remove any leftover *.mp4.tmp files from a previous run that crashed
# before the temp file could be renamed to its final location.
derived_root = Path(processed_root, "derived")
if derived_root.exists():
for tmp_file in derived_root.glob('**/*.tmp.mp4'):
try:
tmp_file.unlink()
logger.info(f"Removed stale temp transcode file: {tmp_file}")
except OSError as ex:
logger.warning(f"Could not remove stale temp file {tmp_file}: {ex}")

# Track corrupt videos to skip remaining heights for that video
corrupt_video_ids = set()

Expand Down
95 changes: 69 additions & 26 deletions app/server/fireshare/util.py
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@
import glob
import shutil
import re
import threading
from datetime import datetime

# Corruption indicators to detect during video validation
Expand Down Expand Up @@ -606,6 +607,8 @@ def run_ffmpeg_with_progress(cmd, total_duration, timeout_seconds=None, data_pat

If data_path is provided, reads the existing status file and updates it with
percent/speed. Progress is throttled to every 0.5 seconds to avoid I/O overhead.
stderr is drained in a background thread to prevent pipe buffer deadlock and
is logged at warning level if the process exits with a non-zero code.
"""
# Insert -progress pipe:1 before output file (last arg)
cmd_with_progress = cmd[:-1] + ['-progress', 'pipe:1'] + [cmd[-1]]
Expand All @@ -616,6 +619,15 @@ def run_ffmpeg_with_progress(cmd, total_duration, timeout_seconds=None, data_pat
percent = None
current_seconds = 0

# Drain stderr in a background thread to prevent pipe buffer from filling
# and blocking ffmpeg. Collected lines are logged on failure.
stderr_lines = []
def _drain_stderr():
for line in process.stderr:
stderr_lines.append(line.rstrip())
stderr_thread = threading.Thread(target=_drain_stderr, daemon=True)
stderr_thread.start()

# -progress outputs clean key=value lines:
# out_time_us=83450000
# speed=1.5x
Expand Down Expand Up @@ -671,6 +683,13 @@ def run_ffmpeg_with_progress(cmd, total_duration, timeout_seconds=None, data_pat
process.kill()
process.wait()
raise
finally:
stderr_thread.join(timeout=5)

if process.returncode != 0 and stderr_lines:
logger.warning(f"FFmpeg exited with code {process.returncode}. stderr output:")
for line in stderr_lines[-100:]:
logger.warning(f" ffmpeg: {line}")

return process

Expand Down Expand Up @@ -737,23 +756,36 @@ def transcode_video_quality(video_path, out_path, height, use_gpu=False, timeout

# Determine output container based on codec
out_path_str = str(out_path)


# Write to a temp path during transcoding; only rename to the final path on
# success. This ensures a partially-written file from a crashed ffmpeg process
# is never picked up and served as a valid transcode output.
tmp_path = out_path.parent / (out_path.stem + '.tmp.mp4')
tmp_path_str = str(tmp_path)
if tmp_path.exists():
try:
tmp_path.unlink()
logger.debug(f"Cleaned up leftover temp file: {tmp_path_str}")
except OSError as ex:
logger.debug(f"Could not remove leftover temp file: {ex}")

mode = 'gpu' if use_gpu else 'cpu'

# Use cached encoder if available to avoid redundant encoder detection during bulk transcoding.
if _working_encoder_cache[mode] is not None:
encoder = _working_encoder_cache[mode]
logger.debug(f"Using cached {mode.upper()} encoder: {encoder['name']}")

# Build ffmpeg command using the cached encoder
logger.info(f"Transcoding video to {height}p using {encoder['name']}")
cmd = _build_transcode_command(video_path, out_path, height, encoder)
cmd = _build_transcode_command(video_path, tmp_path, height, encoder)

logger.debug(f"$: {' '.join(cmd)}")

try:
result = run_ffmpeg_with_progress(cmd, total_duration, timeout_seconds, data_path)
if result.returncode == 0:
tmp_path.rename(out_path)
e = time.time()
logger.info(f'Transcoded {str(out_path)} to {height}p in {e-s:.2f}s')
return (True, None)
Expand All @@ -762,22 +794,32 @@ def transcode_video_quality(video_path, out_path, height, use_gpu=False, timeout
logger.warning(f"Cached encoder {encoder['name']} failed with exit code {result.returncode}")
logger.info("Clearing encoder cache and retrying with all available encoders...")
_working_encoder_cache[mode] = None
if tmp_path.exists():
try:
tmp_path.unlink()
except OSError as cleanup_ex:
logger.debug(f"Could not clean up temp file: {cleanup_ex}")
except sp.TimeoutExpired:
logger.warning(f"Cached encoder {encoder['name']} timed out after {timeout_seconds} seconds")
logger.info("Clearing encoder cache and retrying with all available encoders...")
_working_encoder_cache[mode] = None
# Clean up the process and any partial output
if os.path.exists(out_path_str):
if tmp_path.exists():
try:
os.remove(out_path_str)
logger.debug(f"Cleaned up timed out output file: {out_path_str}")
tmp_path.unlink()
logger.debug(f"Cleaned up timed out temp file: {tmp_path_str}")
except OSError as cleanup_ex:
logger.debug(f"Could not clean up timed out output: {cleanup_ex}")
logger.debug(f"Could not clean up timed out temp file: {cleanup_ex}")
except Exception as ex:
# Cached encoder failed - clear cache and fall through to try all encoders
logger.warning(f"Cached encoder {encoder['name']} failed: {ex}")
logger.info("Clearing encoder cache and retrying with all available encoders...")
_working_encoder_cache[mode] = None
if tmp_path.exists():
try:
tmp_path.unlink()
except OSError as cleanup_ex:
logger.debug(f"Could not clean up temp file: {cleanup_ex}")

# No cached encoder - need to detect a working encoder
# Check if GPU is requested but NVENC is not available in ffmpeg
Expand Down Expand Up @@ -868,20 +910,21 @@ def transcode_video_quality(video_path, out_path, height, use_gpu=False, timeout
# as fallback, so CPU transcoding will be attempted automatically if GPU fails
logger.info(f"Detecting working {mode.upper()} encoder by attempting transcode...")
encoders = _get_encoder_candidates(use_gpu, encoder_preference)

last_exception = None
for encoder in encoders:
logger.info(f"Trying {encoder['name']}...")

# Build ffmpeg command
cmd = _build_transcode_command(video_path, out_path, height, encoder)
# Build ffmpeg command targeting the temp path
cmd = _build_transcode_command(video_path, tmp_path, height, encoder)

logger.debug(f"$: {' '.join(cmd)}")

try:
result = run_ffmpeg_with_progress(cmd, total_duration, timeout_seconds, data_path)
if result.returncode == 0:
# Success! Cache this encoder and return
# Success! Move temp file to final location, cache encoder, and return.
tmp_path.rename(out_path)
logger.info(f"✓ {encoder['name']} works! Using it for all transcodes this session.")
_working_encoder_cache[mode] = encoder
e = time.time()
Expand All @@ -890,33 +933,33 @@ def transcode_video_quality(video_path, out_path, height, use_gpu=False, timeout
else:
logger.warning(f"✗ {encoder['name']} failed with exit code {result.returncode}")
last_exception = Exception(f"Transcode failed with exit code {result.returncode}")
# Clean up failed output file before trying next encoder
if os.path.exists(out_path_str):
# Clean up temp file before trying next encoder
if tmp_path.exists():
try:
os.remove(out_path_str)
logger.debug(f"Cleaned up failed output file: {out_path_str}")
tmp_path.unlink()
logger.debug(f"Cleaned up failed temp file: {tmp_path_str}")
except OSError as cleanup_ex:
logger.debug(f"Could not clean up failed output: {cleanup_ex}")
logger.debug(f"Could not clean up failed temp file: {cleanup_ex}")
except sp.TimeoutExpired:
logger.warning(f"✗ {encoder['name']} timed out after {timeout_seconds} seconds")
last_exception = Exception(f"Transcode timed out after {timeout_seconds} seconds")
# Clean up failed output file before trying next encoder
if os.path.exists(out_path_str):
# Clean up temp file before trying next encoder
if tmp_path.exists():
try:
os.remove(out_path_str)
logger.debug(f"Cleaned up timed out output file: {out_path_str}")
tmp_path.unlink()
logger.debug(f"Cleaned up timed out temp file: {tmp_path_str}")
except OSError as cleanup_ex:
logger.debug(f"Could not clean up timed out output: {cleanup_ex}")
logger.debug(f"Could not clean up timed out temp file: {cleanup_ex}")
except Exception as ex:
logger.warning(f"✗ {encoder['name']} failed: {ex}")
last_exception = ex
# Clean up failed output file before trying next encoder
if os.path.exists(out_path_str):
# Clean up temp file before trying next encoder
if tmp_path.exists():
try:
os.remove(out_path_str)
logger.debug(f"Cleaned up failed output file: {out_path_str}")
tmp_path.unlink()
logger.debug(f"Cleaned up failed temp file: {tmp_path_str}")
except OSError as cleanup_ex:
logger.debug(f"Could not clean up failed output: {cleanup_ex}")
logger.debug(f"Could not clean up failed temp file: {cleanup_ex}")

# If we get here, no encoder worked
error_msg = f"No working {mode.upper()} encoder found for video. Tried: {', '.join([e['name'] for e in encoders])}"
Expand Down
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