Ppt Audio To Video

Produce slide images.

• If pdf exists, render it to images:

  pdftoppm -png -r 200 "$PDF" "$OUTDIR/slide"
  

• If only pptx exists, export to pdf or slide images with Keynote or PowerPoint, then continue from pdf.
• Keep slide filenames ordered and stable, such as slide-01.png, slide-02.png, ...

Extract slide text.

• Run:

  python3 scripts/extract_slide_outline.py \
    --pptx "$PPTX" \
    --out "$WORKDIR/slide_outline.csv"
  

• Use the output to identify slide titles, distinctive keywords, and section changes.

Extract clean audio for ASR.

• For audio-only mp4, extract mono wav:

  ffmpeg -y -i "$AUDIO_MP4" -ar 16000 -ac 1 -c:a pcm_s16le "$WORKDIR/audio.wav"
  

• If the source is already wav/mp3/m4a, convert to the same mono wav form if needed.

Transcribe with whisper-cli.

• Example:

  whisper-cli -ng \
    -m "$MODEL" \
    -f "$WORKDIR/audio.wav" \
    -l zh \
    -ocsv -osrt -of "$WORKDIR/transcript"
  

• Prefer transcript.csv for downstream parsing. transcript.srt is useful for manual review.
• If GPU allocation fails on macOS, retry with -ng to force CPU mode.

Build slide_timings.csv.

• Do not average slide durations unless the user explicitly asks for it.
• Read the transcript and slide outline together, then create a monotonic timing plan by topic changes, section boundaries, and unique keywords.
• Use this schema:

  slide,start_sec,end_sec,duration_sec,reason
  1,0.000,15.000,15.000,opening title and agenda
  2,15.000,100.000,85.000,architecture overview starts here
  

• Keep slide numbers sequential and ensure duration_sec = end_sec - start_sec.
• Validate that the last end_sec matches the audio duration or is within a small tolerance.

Render the final video.

• Run:

  python3 scripts/render_from_timing_csv.py \
    --images "$SLIDE_IMAGES_DIR" \
    --timings "$WORKDIR/slide_timings.csv" \
    --audio "$WORKDIR/audio.wav" \
    --output "$OUT_VIDEO"
  

• The script generates an ffconcat file, validates timing continuity, and calls ffmpeg to encode the final mp4.

Verify and iterate.

• Check output duration with ffprobe.
• If a slide cuts too early or too late, edit only the affected rows in slide_timings.csv and rerun the render script.
• Keep the transcript, outline, and timing CSV as reproducible working files.