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doc:appunti:linux:video:ffmpeg [2023/01/07 15:20] – [Final rendering (re-encoding)] niccolodoc:appunti:linux:video:ffmpeg [2023/11/13 11:22] – [Final rendering (re-encoding)] niccolo
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 ./kenburst-1-make-images "$INPUT_FILE" "$KBURST_GEO" "$DURATION_S" \ ./kenburst-1-make-images "$INPUT_FILE" "$KBURST_GEO" "$DURATION_S" \
     | ./kenburst-2-make-video "$OUTPUT_MP4"     | ./kenburst-2-make-video "$OUTPUT_MP4"
-</code> 
- 
-====== Final rendering (re-encoding) ====== 
- 
-The video stream recorded by the Xiaomi Yi camera is **1920x1080 pixels** at a variable bitrate of **12.0 Mb/s**. Because we watch it on a simple TV set capable only of 1366x768 pixels, we we re-encode it with the following settings: 
- 
-^ Video codec     | MPEG-4 AVC (x264)  | 
-^ Video filter    | swresize, 1366x768, Bilinear  | 
-^ Basic x264      | Preset: **slow** (or less), Tuning: **film**, Profile: **High**, IDC Level: **Auto** | 
-^ Video encoding  | Average Bitrate (Two Pass), Average Bitrate 4096 kb/s (about 1.8 Gb per hour)  | 
-^ Audio codec     | <del>Lame MP3</del> Vorbis  | 
-^ Audio bitrate   | CBR 192 (or higher)  | 
- 
-We can use **Avidemux** to make the final rendering (re-encoding). For a **command line only** solution you can consider **ffmpeg** to perfomr the re-encoding and to make the merge (mux) all into a Matroska container. 
- 
-<code bash> 
-#!/bin/sh 
-TITLE="Balcani, maggio 2022" 
-ffmpeg \ 
-    -i "video-high-quality.mkv" \ 
-    -i 'audio-music.ogg' -i 'audio-live.ogg' \ 
-    -map '0:v:0' -map '1:a:0' -map '2:a:0' \ 
-    -metadata title="$TITLE" -metadata:s:v:0 title="$TITLE" \ 
-    -metadata:s:a:0 title="Accompagnamento musicale" \ 
-    -metadata:s:a:1 title="Audio in presa diretta" \ 
-    -filter:v "scale=1366x768" -aspect "16:9" \ 
-    -vcodec 'libx264' -pix_fmt 'yuvj420p' -preset 'veryslow' -tune 'film' -profile:v 'high' -level:v 5 \ 
-    -acodec copy \ 
-    "2022-05_balcani.mkv" 
 </code> </code>
  
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 The gamma correction for the three RGB channels was determined with the GIMP, using the //Colors// => //Levels// => //Pick the gray point for all channels// tool. The use of MPEG-TS clips allowed the montage of the final video by just concatenating them. The gamma correction for the three RGB channels was determined with the GIMP, using the //Colors// => //Levels// => //Pick the gray point for all channels// tool. The use of MPEG-TS clips allowed the montage of the final video by just concatenating them.
  
-==== AVC (x264) is better than ASP (xvid4) ====+===== AVC (x264) is better than ASP (xvid4) =====
  
 See this page: **[[https://www.avidemux.org/admWiki/doku.php?id=general:common_myths|Common myths]]** to understand the differences between formats (standards) and codecs (pieces of software). Read also this simple page: **[[https://www.cyberlink.com/support/product-faq-content.do?id=1901|Difference between MPEG-4 AVC and MPEG-4 ASP]]**. See also the Wikipedia article about **[[wp>Advanced Video Coding]]**. See this page: **[[https://www.avidemux.org/admWiki/doku.php?id=general:common_myths|Common myths]]** to understand the differences between formats (standards) and codecs (pieces of software). Read also this simple page: **[[https://www.cyberlink.com/support/product-faq-content.do?id=1901|Difference between MPEG-4 AVC and MPEG-4 ASP]]**. See also the Wikipedia article about **[[wp>Advanced Video Coding]]**.
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 </code> </code>
  
 +====== ffmpeg: leggere la sequenza di VOB da un DVD ======
 +
 +Nella directory **VIDEO_TS** di un DVD la traccia principale è normalmente suddivisa in file numerati sequenzialmente, ad esempio: ''VTS_01_0.VOB'', ''VTS_01_1.VOB'', ...
 +
 +In teoria è sufficiente concatenare i file in un solo file destinazione e quindi trattarlo come un normale file audio/video. Tuttavia è possibile indicare i singoli file come input senza la necessità di occupare ulteriore spazio disco con questa sintassi:
 +
 +<code bash>
 +SOURCE="concat:VTS_01_1.VOB|VTS_01_2.VOB|VTS_01_3.VOB|VTS_01_4.VOB|VTS_01_5.VOB"
 +ffmpeg -i "$SOURCE" ...
 +</code>
 +
 +====== ffmpeg: impostare un ritardo sui sottotitoli durante il muxing ======
 +
 +Se un flusso di sottotitoli (ad esempio nel formato Picture based DVD) non indica correttamente l'offset iniziale di riproduzione è possibile dire ad ffmpeg di impostarlo opportunamente in fase di muxing. In questo esempio il primo sottotitolo appare a 44.5 secondi:
 +
 +<code bash>
 +ffmpeg -i video-stream.mkv -i audio-stream.mkv -itsoffset 44.5 -i subtitles-stream.mkv ...
 +</code>
 +
 +In generale dovrebbe essere possibile scoprire l'offset quando ffmpeg legge l'intero stream, al momento in cui trova il prmio frame dei subtitles mostra qualcosa del genere sulla console:
 +
 +<code>
 +[mpeg @ 0x55f98bb2c6c0] New subtitle stream 0:7 at pos:14755854 and DTS:44.5s
 +</code>
  
 ====== Doppiaggio audio con Ardour ====== ====== Doppiaggio audio con Ardour ======
  
 Vedere la pagina dedicata: **[[ardour_dubbing]]**. Vedere la pagina dedicata: **[[ardour_dubbing]]**.
doc/appunti/linux/video/ffmpeg.txt · Last modified: 2023/11/13 11:24 by niccolo