DOC SHOP TRANSCODING PROCESS
About This Document
The following document will describe how to convert a film into the format used by Hot Docs for Doc
Shop viewing. As well, it will explain how to submit the converted film to Hot Docs' server.
Hot Docs' Doc Shop is a browser-based application used to find and play online the movies received from
filmmakers for this year's festival. Hot Docs displays all film submissions in Flash Video (FLV) format.
When a film DVD is received by Hot Docs, it is converted from DVD format to FLV. This conversion
process is called transcoding. The transcoding can only take place if the DVD has no copy/file
Hot Docs uses an automated process to convert the DVD into the FLV file. Transcoding is inherently
lossy, meaning there is some degradation in the video/audio quality. Film makers may want to create
the FLV file themselves to ensure that the quality of the FLV film is acceptable.
There are numerous software packages on the market which can be used to transcode the video.
Before a DVD can be converted into an FLV, it usually must be converted into an intermediate format,
such as AVI or MPG. Often, the same software a film maker uses to create a DVD can convert the video
into such a format (i.e. AVI, MPG). For Windows users, there is a free application which can be used to
convert a DVD into a single MPG file: Vob2Mpg. This is available at
http://software.badgerit.com/VOB2MPG.html. Another application, for Mac/Windows/Linux operating
systems, is Handbrake, available at http://handbrake.fr/?article=download.
FLV transcoding software comes is available in both open-source (free) and licensed versions. These
applications can convert files from a video format to Flash Video. They allow you to customize various
parameters that affect the quality of the converted video. The minimum parameters recommended by
Hot Docs can be found in Section A.
The Hot Docs' Doc Shop displays a static image associated with each film. When you submit an FLV
file of the DVD submission, you should also supply two accompanying image files. The specifications for
these images can be found in Section A.
Once the film has been converted into an FLV file, and accompanying images have been created, you can
deliver the files to Hot Docs. The simplest and quickest method for sending the files is through ftp.
Another method is to burn the files to a CD and mail that CD to Hot Docs.
Summary of Steps for sending Hot Docs a transcoded video
1. Convert the DVD into a single video file, i.e. AVI, MPG
2. Transcode the video file into an FLV file
3. Test the FLV file to make sure it is viewable
4. Create 2 image files of the video
5. Correctly name the files before sending
6. FTP or mail the files to Hot Docs
The rest of this document will detail the above steps, with the following constraints:
- DVD Conversion to MPG using Vob2Mpg on a Windows-based system
- Transcoding the MPG file into an FLV file using ffmpeg on a Windows-based system
- Creating 2 screenshots of the video using ffmpeg on a Windows-based system
- Using FTP to transfer the 3 files (video FLV file and the 2 image files) to the Hot Docs server
SECTION A: Technical Specifications of Files to Send to Hot Docs
As previously noted, other applications and methods exist for transcoding a DVD film into a
single FLV file, and for creating image files. Provided that the technical specifications listed
below are met, any method can be used to create the 3 files:
Video Codec: Sorenson Spark (or On2 VP6, which has higher quality video output)
Bit Rate: 1000 kbps
Frame Per Second (FPS):25
Width = 640 pixels
Height = (the value that maintains the original aspect ratio)
Audio format: MP3
Data rate: 48kbps
Audio rate: 22050 Hz
Image files specifications
File Type: JPG
Dimensions: 60 x 50 AND 400 x 300
If you have created these 3 files using other means, and do not need to consult the Detailed
Steps section of the document, please refer to the section on File Names (Section F), so that
the files are correctly named, and then refer to Section G, on sending the files to the Hot Docs
Detailed Steps to create the 3 files to send to Hot Docs (Sections B-G)
SECTION B: Convert the DVD into a single MPG file (Windows)
This section can be skipped if you have already converted the video into a single video file,
such as AVI or MPG.
The application that will be used to convert the DVD into an MPG file is Vob2Mpg, and can
be downloaded here:
Once you have installed Vob2Mpg, launch the application. It has two fields: one for the input
DVD folder, and one for the output folder. Before proceeding, make sure the DVD is inserted
in the DVD-ROM drive. For the input field, point it to the DVD's drive and then into the
VIDEO_TS folder. That is where the video files (.VOB) are located. Set the output folder to
somewhere on the computer, i.e. c:hotdocs. Click 'Start' to begin the process. A 2 hours
movie should take approximately 8 - 10 minutes to convert into an MPG file. This process
maintains the audio and video quality of the original DVD. When the process is complete, you
should have a file in the output folder named something like: VTS_01.mpg
SECTION C: Transcode MPG file into FLV (Windows)
You can skip this section if you have already converted the MPG file into an FLV file.
Before transcoding the MPG into FLV, you will need to know the aspect ratio of the video.
Two common ratios are 16:9 and 4:3. The aspect ratio is needed to calculate the height
value when transcoding. The width value is fixed at 640 pixels. The width value is calculated
based on the aspect ratio. For example, the ratio 16:9, with a width of 640, has a calculated
height of 360. The aspect ratio 4:3, with the fixed width value of 640, has a calculated height
The application that will be used to convert the MPG file into a Flash video file (FLV) is
ffmpeg. The latest version is (unofficially) available here for download:
http://tripp.arrozcru.org/. The download is in a compressed format, so you may also need to
download and install an unzip program, such as 7zip (http://www.7-zip.org/download.html) to
uncompress the ffmpeg installation files.
Once you have uncompressed the ffmpeg executable, follow the following steps:
1) open a command-line window, by clicking on Start --> Run, and then enter (without
the quotes) quot;cmdquot; and then press <ENTER>. A command line window should open,
typically at c:Documents and SettingsUSERNAME.
2) Using the DOS quot;cdquot; command, change to the folder where ffmpeg is installed, i.e. quot;cd
c:HotDocsffmpegquot; and then press <ENTER>. To test if you have properly changed
to the correct folder, type in quot;ffmpegquot; and press <ENTER>. You should see ffmpeg
related text scroll down the screen. If you do not see it, verify the location where
ffmpeg was extracted to, and that you have typed the folder location correctly
3) The following command will transcode the MPG file into a Flash file:
ffmpeg -i quot;c:HotDocsVTS_01.mpgquot; -pass 1 -g 240 -qcomp 0.6 -qmax 15 -
qdiff 4 -i_qfactor 0.71428572 -b_qfactor 0.76923078 -maxrate 1000k -
bufsize 1200k -s 640x480 -b 1000k -refs 5 -subq 6 -r 25 -ab 32k -ar 22050
-ac 1 MyFilm.flv
Before entering it, replace the following values:
- replace the path of the MPG file with your path, eg: quot;c:HotDocsVTS_01.mpgquot;
- replace the width value with the calculated width value eg: 640x480, or
Once you have entered the command and replaced the necessary values, press <ENTER> to
begin the transcoding process. It will take a few minutes, and longer videos take longer to
transcode. When the process is completed, you will find the file quot;MyFilm.flvquot; in the folder
where ffmpeg was run from.
SECTION D: Testing the FLV file (Windows)
Please verify that the FLV file created is viewable and is acceptable to the filmmaker. In
order to do this, you will need to open the FLV file with an FLV player. There are many free
FLV players available on the web. Among them are Riva FLV Player
(http://www.download.com/Riva-FLV-Player/3000-2139_4-127804.html) and FLV Player
(http://www.download.com/FLV-Player/3000-13632_4-10467081.html). View the FLV file
with the player to make sure it has adequate audio and video. Since the process of
transcoding is lossy, there will be a degradation of audio and video. This is especially true if
the film has much action (i.e. fast moving subjects). Possible scenarios when viewing the
- If there is no audio and/or video, redo the transcoding process.
- If the quality is less than desirable, view the sample Hot Docs video located at
http://hotdocs.ca/SampleVideo. This will provide a basis for comparison, and what to
expect in a transcoded flv video. Reading the ffmpeg manual and tweaking some
values can change the quality of the video
- If after redoing the transcoding process, the file is not viewable or has no audio, send
the DVD to Hot Docs for transcoding by Hot Docs.
SECTION E: Extracting screenshots from the video (Windows)
The Doc Shop requires two image files (JPG format) for each film, each displaying the same
image, but having different size dimensions. It is recommended that the image be a frame
from the film. When Hot Docs receives a DVD, we select a random frame and create 2 image
files. Having the filmmaker select the frame ensures that an appropriate image represents the
film. Any method can be used to create the two image files, but they must adhere to the size
dimensions mentioned in the Overview [60 x 50 AND 400 x 300].
The following steps show how to use ffmpeg to extract the image files:
NOTE: The images are identical in content, but are different sizes
1) open a command-line window, by clicking on Start --> Run, and then enter (without the
quotes) quot;cmdquot; and then press <ENTER>
2) A command line window should open, typically at c:Documents and
SettingsUSERNAME. Using the DOS quot;cdquot; command, change to the folder where ffmpeg
is installed, i.e. quot;cd c:HotDocsffmpegquot; and then press <ENTER>. To test if you have
properly changed to the correct folder, type in quot;ffmpegquot; and press <ENTER>. You should
see ffmpeg related text scroll down the screen. If you do not see it, verify the location for
ffmpeg, and that you have typed the folder location correctly
- Enter the following command to create a 60x50 jpg file, replacing H,MM, and
SS with the hour, minutes, and seconds of the frame you want captured (the
command can take up to a few minutes to run as it extracts the image):
- ffmpeg -i quot;c:HotDocsVTS_01.mpgquot; -ss H:MM:SS.00 -sameq -vframes 1 -s
- For example, the following command captures the frame at 41 minutes and 10
seconds: ffmpeg -i quot;c:HotDocsVTS_01.mpgquot; -ss 0:41:10.00 -sameq -vframes
1 -s 60x50 x%01d_small.jpg
3) Enter the following command to create a 400x300 jpg file, replacing H,MM, and SS with
the hour, minutes, and seconds of the frame you want captured (use the same time values
as used in step 2 above:
- ffmpeg -i quot;c:HotDocsVTS_01.mpgquot; -ss H:MM:SS.00 -sameq -vframes 1 -s
SECTION F: File Naming
When Hot Docs receives the files (the 2 image files and the FLV file), we need to know which
film these files belong to. Upon submitting the film entry on the web (by filling out the online
Hot Docs form), you should have received a Film ID. This is a 5-digit number used to denote
the film. If you do not have one, please contact Hot Docs at firstname.lastname@example.org to
retrieve the Film ID. The 3 files can only be mailed or uploaded with that 5-digit value.
The files should be named in the following manner:
- FLV : FILMID_2.flv (example: 12345_2.flv)
- JPG image A (60x50) : FILMID_a.jpg (example: 12345_a.jpg)
- JPG image B (400x300) : FILMID_b.jpg (example: 12345_b.jpg)
SECTION G: Sending the files to Hot Docs
There are to two methods to send the files to Hot Docs:
2) FTP (uploading to Hot Docs' server)
Sending by mail:
- Burn the 3 files to a CD/DVD
- Label the disc with the FilmID
- Mail it to the Hot Docs address
FTP the file:
You will need an FTP client to perform this step. Most web browsers have built-in ftp clients,
and there are free ones available, such as FileZilla ( http://filezilla-
project.org/download.php). You will need to login to connect to the Hot Docs server to
upload (send) the files. Once you login, by entering the username and password below, you
will need to change to the quot;incomingquot; folder, and then copy the 3 files to the incoming folder.
Since the FLV file will be large, the upload could take quite a while (in some cases, over an
hour). To verify the files were sent correctly, check that the file sizes of the files uploaded
match the files on your machine. If they do not match, you will need to upload the files again.
Due to security concerns, in order to resend a file, you will have to contact
email@example.com and notify them that a film file is incomplete, and needs to be resent.