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Autres articles (77)
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MediaSPIP v0.2
21 juin 2013, parMediaSPIP 0.2 est la première version de MediaSPIP stable.
Sa date de sortie officielle est le 21 juin 2013 et est annoncée ici.
Le fichier zip ici présent contient uniquement les sources de MediaSPIP en version standalone.
Comme pour la version précédente, il est nécessaire d’installer manuellement l’ensemble des dépendances logicielles sur le serveur.
Si vous souhaitez utiliser cette archive pour une installation en mode ferme, il vous faudra également procéder à d’autres modifications (...) -
Mise à disposition des fichiers
14 avril 2011, parPar défaut, lors de son initialisation, MediaSPIP ne permet pas aux visiteurs de télécharger les fichiers qu’ils soient originaux ou le résultat de leur transformation ou encodage. Il permet uniquement de les visualiser.
Cependant, il est possible et facile d’autoriser les visiteurs à avoir accès à ces documents et ce sous différentes formes.
Tout cela se passe dans la page de configuration du squelette. Il vous faut aller dans l’espace d’administration du canal, et choisir dans la navigation (...) -
Le profil des utilisateurs
12 avril 2011, parChaque utilisateur dispose d’une page de profil lui permettant de modifier ses informations personnelle. Dans le menu de haut de page par défaut, un élément de menu est automatiquement créé à l’initialisation de MediaSPIP, visible uniquement si le visiteur est identifié sur le site.
L’utilisateur a accès à la modification de profil depuis sa page auteur, un lien dans la navigation "Modifier votre profil" est (...)
Sur d’autres sites (6818)
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Evolution #4042 (Nouveau) : Forums : pouvoir les reoodonner
6 novembre 2017, par Maïeul RouquetteIl arrive fréquemment que des personnes se trompent en répondant à un message de forum, en créant par exemple un nouveau thread au lieu de prolonger l’ancien.
Ce serait pas mal d’avoir un outils pour réoordonner dans l’espace privé ces forums. Par contre aucune idée de l’ergonomie que cela pourrait prendre,
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Why does the frame count change when scaling with FFmpeg ?
22 octobre 2016, par ajmicekI use this to scale 1920x1080 H.264 videos :
ffmpeg -i IMG_1438.MOV -threads 2 -vf scale=-2:600 IMG_1438_scaledTo600.MOVAnd it works great ! But here is my question : most of the time, the frame rate stays exactly the same between the original file and the scaled file. For example :
$ mediainfo -F IMG_1426.MOV | grep Frame\ rate
Frame rate : 29.970
Frame rate : 29.970 FPS
Frame rate mode : VFR
Frame rate mode : Variable
Frame rate : 29.970
Frame rate : 29.970 (29970/1000) FPS
$ mediainfo -F IMG_1426_scaledTo600.MOV | grep Frame\ rate
Frame rate : 29.970
Frame rate : 29.970 FPS
Frame rate mode : CFR
Frame rate mode : Constant
Frame rate : 29.970
Frame rate : 29.970 (30000/1001) FPSBut sometimes, the frame rate increases dramatically :
$ mediainfo -F IMG_1438.MOV | grep Frame\ rate
Frame rate : 25.044
Frame rate : 25.044 FPS
Frame rate mode : VFR
Frame rate mode : Variable
Frame rate : 25.044
Frame rate : 25.044 FPS
$ mediainfo -F IMG_1438_scaledTo600.MOV | grep Frame\ rate
Frame rate : 120.000
Frame rate : 120.000 FPS
Frame rate mode : CFR
Frame rate mode : Constant
Frame rate : 120.000
Frame rate : 120.000 FPSWhat should I know about FFmpeg or libx264 or libswscale that will help me understand why this happens ? (Hoping to hear from LordNeckbeard, in particular).
mediainfo IMG_1438.MOV --Fulloutputs :General
Count : 327
Count of stream of this kind : 1
Kind of stream : General
Kind of stream : General
Stream identifier : 0
Count of video streams : 1
Count of audio streams : 1
OtherCount : 2
Video_Format_List : AVC
Video_Format_WithHint_List : AVC
Codecs Video : AVC
Audio_Format_List : AAC
Audio_Format_WithHint_List : AAC
Audio codecs : AAC LC
Complete name : IMG_1438.MOV
File name : IMG_1438
File extension : MOV
Format : MPEG-4
Format : MPEG-4
Format/Extensions usually used : mp4 m4v m4a m4b m4p 3gpp 3gp 3gpp2 3g2 k3g jpm jpx mqv ismv isma f4v
Commercial name : MPEG-4
Format profile : QuickTime
Internet media type : video/mp4
Codec ID : qt
Codec ID : qt 0000.00 (qt )
Codec ID/Url : http://www.apple.com/quicktime/download/standalone.html
CodecID_Version : 0000.00
CodecID_Compatible : qt
Codec : MPEG-4
Codec : MPEG-4
Codec/Extensions usually used : mp4 m4v m4a m4b m4p 3gpp 3gp 3gpp2 3g2 k3g jpm jpx mqv ismv isma f4v
File size : 113990140
File size : 109 MiB
File size : 109 MiB
File size : 109 MiB
File size : 109 MiB
File size : 108.7 MiB
Duration : 52268
Duration : 52 s 268 ms
Duration : 52 s 268 ms
Duration : 52 s 268 ms
Duration : 00:00:52.268
Duration : 00:00:52:09
Duration : 00:00:52.268 (00:00:52:09)
Overall bit rate : 17447026
Overall bit rate : 17.4 Mb/s
Frame rate : 25.044
Frame rate : 25.044 FPS
Frame count : 1309
Stream size : 56670
Stream size : 55.3 KiB (0%)
Stream size : 55 KiB
Stream size : 55 KiB
Stream size : 55.3 KiB
Stream size : 55.34 KiB
Stream size : 55.3 KiB (0%)
Proportion of this stream : 0.00050
HeaderSize : 28
DataSize : 113966271
FooterSize : 23841
IsStreamable : No
Encoded date : UTC 2016-10-08 22:51:19
Tagged date : UTC 2016-10-08 22:52:12
File last modification date : UTC 2016-10-08 22:51:19
File last modification date (local) : 2016-10-08 17:51:19
Writing library : Apple QuickTime
Writing library : Apple QuickTime
Encoded_Library_Name : Apple QuickTime
com.apple.quicktime.make : Apple
com.apple.quicktime.model : iPhone 5
com.apple.quicktime.software : 10.0.2
com.apple.quicktime.creationdate : 2016-10-08T17:51:19-0500
Video
Count : 334
Count of stream of this kind : 1
Kind of stream : Video
Kind of stream : Video
Stream identifier : 0
StreamOrder : 0
ID : 1
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format/Url : http://developers.videolan.org/x264.html
Commercial name : AVC
Format profile : High@L4.1
Format settings : CABAC / 1 Ref Frames
Format settings, CABAC : Yes
Format settings, CABAC : Yes
Format settings, ReFrames : 1
Format settings, ReFrames : 1 frame
Internet media type : video/H264
Codec ID : avc1
Codec ID/Info : Advanced Video Coding
Codec ID/Url : http://www.apple.com/quicktime/download/standalone.html
Codec : AVC
Codec : AVC
Codec/Family : AVC
Codec/Info : Advanced Video Codec
Codec/Url : http://developers.videolan.org/x264.html
Codec/CC : avc1
Codec profile : High@L4.1
Codec settings : CABAC / 1 Ref Frames
Codec settings, CABAC : Yes
Codec_Settings_RefFrames : 1
Duration : 52268
Duration : 52 s 268 ms
Duration : 52 s 268 ms
Duration : 52 s 268 ms
Duration : 00:00:52.268
Duration : 00:00:52:09
Duration : 00:00:52.268 (00:00:52:09)
Bit rate : 17375530
Bit rate : 17.4 Mb/s
Width : 1920
Width : 1 920 pixels
Height : 1080
Height : 1 080 pixels
Stored_Height : 1088
Sampled_Width : 1920
Sampled_Height : 1080
Pixel aspect ratio : 1.000
Display aspect ratio : 1.778
Display aspect ratio : 16:9
Rotation : 90.000
Rotation : 90°
Frame rate mode : VFR
Frame rate mode : Variable
Frame rate : 25.044
Frame rate : 25.044 FPS
Minimum frame rate : 23.077
Minimum frame rate : 23.077 FPS
Maximum frame rate : 30.000
Maximum frame rate : 30.000 FPS
Frame count : 1309
Resolution : 8
Resolution : 8 bits
Colorimetry : 4:2:0
Color space : YUV
Chroma subsampling : 4:2:0
Chroma subsampling : 4:2:0
Bit depth : 8
Bit depth : 8 bits
Scan type : Progressive
Scan type : Progressive
Interlacement : PPF
Interlacement : Progressive
Bits/(Pixel*Frame) : 0.335
Stream size : 113523046
Stream size : 108 MiB (100%)
Stream size : 108 MiB
Stream size : 108 MiB
Stream size : 108 MiB
Stream size : 108.3 MiB
Stream size : 108 MiB (100%)
Proportion of this stream : 0.99590
Title : Core Media Video
Encoded date : UTC 2016-10-08 22:51:19
Tagged date : UTC 2016-10-08 22:52:12
Color range : Limited
colour_description_present : Yes
Color primaries : BT.709
Transfer characteristics : BT.709
Matrix coefficients : BT.709
Audio
Count : 272
Count of stream of this kind : 1
Kind of stream : Audio
Kind of stream : Audio
Stream identifier : 0
StreamOrder : 1
ID : 2
ID : 2
Format : AAC
Format/Info : Advanced Audio Codec
Commercial name : AAC
Format profile : LC
Codec ID : 40
Codec : AAC LC
Codec : AAC LC
Codec/Family : AAC
Codec/CC : 40
Duration : 52268
Duration : 52 s 268 ms
Duration : 52 s 268 ms
Duration : 52 s 268 ms
Duration : 00:00:52.268
Duration : 00:00:52:15
Duration : 00:00:52.268 (00:00:52:15)
Source duration : 52338
Source duration : 52 s 338 ms
Source duration : 52 s 338 ms
Source duration : 52 s 338 ms
Source duration : 00:00:52.338
Bit rate mode : CBR
Bit rate mode : Constant
Bit rate : 64000
Bit rate : 64.0 kb/s
Channel(s) : 1
Channel(s) : 1 channel
Channel positions : Front: C
Channel positions : 1/0/0
ChannelLayout : C
Samples per frame : 1024
Sampling rate : 44100
Sampling rate : 44.1 kHz
Samples count : 2305019
Frame rate : 43.066
Frame rate : 43.066 FPS (1024 spf)
Frame count : 2251
Source frame count : 2254
Compression mode : Lossy
Compression mode : Lossy
Stream size : 410424
Stream size : 401 KiB (0%)
Stream size : 401 KiB
Stream size : 401 KiB
Stream size : 401 KiB
Stream size : 400.8 KiB
Stream size : 401 KiB (0%)
Proportion of this stream : 0.00360
Source stream size : 410894
Source stream size : 401 KiB (0%)
Source stream size : 401 KiB
Source stream size : 401 KiB
Source stream size : 401 KiB
Source stream size : 401.3 KiB
Source stream size : 401 KiB (0%)
Source_StreamSize_Proportion : 0.00360
Title : Core Media Audio
Encoded date : UTC 2016-10-08 22:51:19
Tagged date : UTC 2016-10-08 22:52:12
Other #1
Count : 112
Count of stream of this kind : 2
Kind of stream : Other
Kind of stream : Other
Stream identifier : 0
Stream identifier : 1
Type : meta
Duration : 52268
Duration : 52 s 268 ms
Duration : 52 s 268 ms
Duration : 52 s 268 ms
Duration : 00:00:52.268
Duration : 00:00:52.268
Frame count : 6
Bit rate mode : VBR
Other #2
Count : 112
Count of stream of this kind : 2
Kind of stream : Other
Kind of stream : Other
Stream identifier : 1
Stream identifier : 2
Type : meta
Duration : 52268
Duration : 52 s 268 ms
Duration : 52 s 268 ms
Duration : 52 s 268 ms
Duration : 00:00:52.268
Duration : 00:00:52.268
Frame count : 1
Bit rate mode : CBRand
ffprobe IMG_1438.MOVoutputs :ffprobe version 3.1.3 Copyright (c) 2007-2016 the FFmpeg developers
built with Apple LLVM version 7.3.0 (clang-703.0.31)
configuration: --prefix=/usr/local/Cellar/ffmpeg/3.1.3 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-opencl --enable-libx264 --enable-libmp3lame --enable-libxvid --disable-lzma --enable-vda
libavutil 55. 28.100 / 55. 28.100
libavcodec 57. 48.101 / 57. 48.101
libavformat 57. 41.100 / 57. 41.100
libavdevice 57. 0.101 / 57. 0.101
libavfilter 6. 47.100 / 6. 47.100
libavresample 3. 0. 0 / 3. 0. 0
libswscale 4. 1.100 / 4. 1.100
libswresample 2. 1.100 / 2. 1.100
libpostproc 54. 0.100 / 54. 0.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'IMG_1438.MOV':
Metadata:
major_brand : qt
minor_version : 0
compatible_brands: qt
creation_time : 2016-10-08 22:51:19
com.apple.quicktime.make: Apple
com.apple.quicktime.model: iPhone 5
com.apple.quicktime.software: 10.0.2
com.apple.quicktime.creationdate: 2016-10-08T17:51:19-0500
Duration: 00:00:52.27, start: 0.000000, bitrate: 17446 kb/s
Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 1920x1080, 17375 kb/s, 25.04 fps, 120 tbr, 600 tbn, 1200 tbc (default)
Metadata:
rotate : 90
creation_time : 2016-10-08 22:51:19
handler_name : Core Media Data Handler
encoder : H.264
Side data:
displaymatrix: rotation of -90.00 degrees
Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, mono, fltp, 62 kb/s (default)
Metadata:
creation_time : 2016-10-08 22:51:19
handler_name : Core Media Data Handler
Stream #0:2(und): Data: none (mebx / 0x7862656D), 0 kb/s (default)
Metadata:
creation_time : 2016-10-08 22:51:19
handler_name : Core Media Data Handler
Stream #0:3(und): Data: none (mebx / 0x7862656D), 0 kb/s (default)
Metadata:
creation_time : 2016-10-08 22:51:19
handler_name : Core Media Data Handler
Unsupported codec with id 0 for input stream 2
Unsupported codec with id 0 for input stream 3UPDATE
To clarify : my video above, the one with the high framerate (120 FPS) output after scaling, plays perfectly before and after scaling with FFmpeg (no sync issues, and 120 FPS is only about 14% larger in file size), I am simply trying to understand why this increase in framerate happens (just a little beyond Mulvya’s note that the framerate stored in the container is wrong).From a programming perspective, the initial issue I ran into was that I was using
frame=from FFmpeg’s sterr console output to determine progress, which reports erroneous results when the frame count increases dramatically on output ("I’m 372% done encoding ?!") ; I have since read another stackoverflow answer and changed my code to usetime=, which appears to be a more robust way for me to display FFmpeg progress. (Also, there is FFmpeg’s-progressoption, of course).Improving on the original command
My new command to scale, preserve a useful framerate, and optimize threads :
ffmpeg -i IMG_1438.MOV -vf scale=-2:600 -r 30 -vsync 0 IMG_1438_scaledTo600.MOVWhere
30is the "Maximum frame rate" frommediainfo.Thanks to help in the comments, I now know I do not fully understand FFmpeg’s use of three different time bases for timestamps :
tbn,tbc, andtbr.
They were explained by Robert Swain in 2009 and his explanation was also used to answer a Stackoverflow question about tbn, tbc, tbr.It sounds to me, as I’m pulling together comments from Mulvya below and Michael Rampe at another forum, that
tbris guessed ; it is frequently but not always the best value to use when changing from a variable to a constant frame rate video.Which leaves these 2 questions...
(1)
tbris incorrect when "field rate and frame rate" differ ? Does this happen a lot ?
(2) Is-r 30where30is the maximum frame rate reported bymediainfothe best way to do it for most codec/container combinations ? (Or should I only use this method when I am scaling a H.264/MPEG-4 AVC video ?) -
Sequencing MIDI From A Chiptune
28 avril 2013, par Multimedia Mike — Outlandish BrainstormsThe feature requests for my game music appreciation website project continue to pour in. Many of them take the form of “please add player support for system XYZ and the chiptune library to go with it.” Most of these requests are A) plausible, and B) in process. I have also received recommendations for UI improvements which I take under consideration. Then there are the numerous requests to port everything from Native Client to JavaScript so that it will work everywhere, even on mobile, a notion which might take a separate post to debunk entirely.
But here’s an interesting request about which I would like to speculate : Automatically convert a chiptune into a MIDI file. I immediately wanted to dismiss it as impossible or highly implausible. But, as is my habit, I started pondering the concept a little more carefully and decided that there’s an outside chance of getting some part of the idea to work.
Intro to MIDI
MIDI stands for Musical Instrument Digital Interface. It’s a standard musical interchange format and allows music instruments and computers to exchange musical information. The file interchange format bears the extension .mid and contains a sequence of numbers that translate into commands separated by time deltas. E.g. : turn key on (this note, this velocity) ; wait x ticks ; turn key off ; wait y ticks ; etc. I’m vastly oversimplifying, as usual.MIDI fascinated me back in the days of dialup internet and discrete sound cards (see also my write-up on the Gravis Ultrasound). Typical song-length MIDI files often ranged from a few kilobytes to a few 10s of kilobytes. They were significantly smaller than the MOD et al. family of tracker music formats mostly by virtue of the fact that MIDI files aren’t burdened by transporting digital audio samples.
I know I’m missing a lot of details. I haven’t dealt much with MIDI in the past… 15 years or so (ever since computer audio became a blur of MP3 and AAC audio). But I’m led to believe it’s still relevant. The individual who requested this feature expressed an interest in being able to import the sequenced data into any of the many music programs that can interpret .mid files.The Pitch
To limit the scope, let’s focus on music that comes from the 8-bit Nintendo Entertainment System or the original Game Boy. The former features 2 square wave channels, a triangle wave, a noise channel, and a limited digital channel. The latter creates music via 2 square waves, a wave channel, and a noise channel. The roles that these various channels usually play typically break down as : square waves represent the primary melody, triangle wave is used to simulate a bass line, noise channel approximates a variety of percussive sounds, and the DPCM/wave channels are fairly free-form. They can have random game sound effects or, if they are to assist in the music, are often used for more authentic percussive sounds.The various channels are controlled via an assortment of memory-mapped hardware registers. These registers are fed values such as frequency, volume, and duty cycle. My idea is to modify the music playback engine to track when various events occur. Whenever a channel is turned on or off, that corresponds to a MIDI key on or off event. If a channel is already playing but a new frequency is written, that would likely count as a note change, so log a key off event followed by a new key on event.
There is the major obstacle of what specific note is represented by a channel in a particular state. The MIDI standard defines 128 different notes spanning 11 octaves. Empirically, I wonder if I could create a table which maps the assorted frequencies to different MIDI notes ?
I think this strategy would only work with the square and triangle waves. Noise and digital channels ? I’m not prepared to tackle that challenge.
Prior Work ?
I have to wonder if there is any existing work in this area. I’m certain that people have wanted to do this before ; I wonder if anyone has succeeded ?Just like reverse engineering a binary program entails trying to obtain a higher level abstraction of a program from a very low level representation, this challenge feels like reverse engineering a piece of music as it is being performed and automatically expressing it in a higher level form.
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