For #WDPD24 and PRONOM Hackathon week this year, I want to find some older formats listed which did not have a signature. There is a list to choose from, but I wanted to find something I hadn’t worked on before. I came across two entries for Real Video:
| PUID | Name | Extension |
| fmt/204 | RealVideo Clip | rv |
| x-fmt/277 | Real Video | rv |
I was familiar with Real Media and Real Audio, but had yet to come across any RealVideo with the RV extension. I thought it would be easy to find some references and samples, but that was not the case. I assume PRONOM originally added these based on MIME types available.
Real or RealNetworks is/was an Internet media company who jumped on the rapidly growing World Wide Web in 1995 to become a leader in Internet Media Delivery. Their initial offerings mainly focused on audio streaming and they accomplished all of this by providing free players and web browser extensions to make it easy to serve up a website with streaming media everyone could enjoy. Later adding video streaming optimized for the slower dialup and connections of the day. They used codecs based on common technology like H.263 and H.264, but used then to make their own proprietary codecs identified through FourCC codes, RV10-RV60.
So thought it would be easy to find a reference to the RV extension, I quickly discovered it wasn’t. Looking at the Wikipedia page on RealVideo, I found no reference to the RV extension. RV is an abbreviation for RealVideo, right? Well, I ended up finding a reference in the RealAudio page under file extensions. Ok, First clue to the existence of the RV extension. The page references RV as being used for video only files and was used by the flagship encoder (RealProducer).
RealProducer was the tool for creating the streaming audio and video formats that could then be used for your website or streaming platform. The RealProducer software came in a Basic version, which was free, and the Plus or Pro version, which was not free and provided more options. The first version of RealProducer to make video files was version 4. I was able to find a copy of the encoder and installed it under a Windows 95 emulator. To my surprise it only saved to the RealMedia RM file format. This format is well known and identified with PRONOM as x-fmt/190 also documented at the LoC.
This was the same with RealProducer 5, 7, 8, 9, and 10 that I was able to try. All made no mention of the RV extension. I was starting to feel this format didn’t exist or that some decided to use the RV extension on their own. Searches on Google yielded a couple results, mostly from users who had found a few files on their older discs and wanted to migrate them to something newer. I was able to find one example, one user shared, but it had the same header as the RealMedia format. The clue was in the file.
hexdump -C ambush_abb.rv 00000000 2e 52 4d 46 00 00 00 12 00 01 00 00 00 00 00 00 |.RMF............| 00000010 00 07 50 52 4f 50 00 00 00 32 00 00 00 03 6e e8 |..PROP...2....n.| 00000020 00 03 6e e8 00 00 03 e0 00 00 01 b3 00 00 6a 6f |..n...........jo| 00000030 00 06 80 fa 00 00 08 b5 00 ba 41 73 00 00 03 55 |..........As...U| 00000040 00 03 00 09 43 4f 4e 54 00 00 00 40 00 00 00 00 |....CONT...@....| 00000050 00 00 00 08 28 43 29 20 32 30 30 35 00 26 00 00 |....(C) 2005.&..| 00000060 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| * 00000270 00 09 61 75 64 69 6f 4d 6f 64 65 00 00 00 02 00 |..audioMode.....| 00000280 06 76 6f 69 63 65 00 00 00 00 2d 00 00 0d 43 72 |.voice....-...Cr| 00000290 65 61 74 69 6f 6e 20 44 61 74 65 00 00 00 02 00 |eation Date.....| 000002a0 13 39 2f 32 30 2f 32 30 30 36 20 31 34 3a 30 37 |.9/20/2006 14:07| 000002b0 3a 30 38 00 00 00 00 53 00 00 0c 47 65 6e 65 72 |:08....S...Gener| 000002c0 61 74 65 64 20 42 79 00 00 00 02 00 3a 52 65 61 |ated By.....:Rea| 000002d0 6c 50 72 6f 64 75 63 65 72 28 52 29 20 42 61 73 |lProducer(R) Bas| 000002e0 69 63 20 31 31 2e 30 20 66 6f 72 20 57 69 6e 64 |ic 11.0 for Wind| 000002f0 6f 77 73 2c 20 42 75 69 6c 64 20 31 31 2e 30 2e |ows, Build 11.0.| 00000300 30 2e 32 30 30 39 00 00 00 00 31 00 00 11 4d 6f |0.2009....1...Mo| 00000310 64 69 66 69 63 61 74 69 6f 6e 20 44 61 74 65 00 |dification Date.| 00000320 00 00 02 00 13 39 2f 32 30 2f 32 30 30 36 20 31 |.....9/20/2006 1| 00000330 34 3a 30 37 3a 30 38 00 00 00 00 1d 00 00 09 76 |4:07:08........v| 00000340 69 64 65 6f 4d 6f 64 65 00 00 00 02 00 07 6e 6f |ideoMode......no| 00000350 72 6d 61 6c 00 44 41 54 41 00 ba 3e 1e 00 00 00 |rmal.DATA..>....|
RealProducer Basic 11 for Windows. The Wikipedia article did hint at this by saying “the latest version of RealProducer reverted to using .ra for audio only files and began using .rv for video files with or without audio.” Why would they use the RM extension for so long, then revert to a different extension with a later version? I found more in the User Manual for version 11.
• .rv – RealVideo
RealProducer uses the .rv file extension if the input is video-only or video-with-audio. You can also select the .rm file extension for video content.
Tip: Using the .rv file extension helps search engines identify the file as a RealVideo clip.
• .rm – RealAudio or RealVideo
RealProducer chooses the .rm file extension if it cannot determine the content of the input clip. You can use .rm file extension for any RealAudio or RealVideo clip, except for variable bit-rate clips.
Ok, so a few things to learn from this. One is the RV extension was used as the default for version 11 as they wanted search engines to identify them as a RealVideo clip. Second thing we learned is there is no difference between the two placeholders in PRONOM, one being a RealVideo file and the other being a RealVideo Clip. We don’t need both.
Now, is there any difference between an RV and RM file?
hexdump -C Producer11-01.rv | head
00000000 2e 52 4d 46 00 00 00 12 00 01 00 00 00 00 00 00 |.RMF............|
00000010 00 07 50 52 4f 50 00 00 00 32 00 00 00 03 6e e8 |..PROP...2....n.|
00000020 00 03 6e e8 00 00 03 e0 00 00 01 c7 00 00 01 66 |..n............f|
00000030 00 00 1b 57 00 00 07 41 00 02 91 0a 00 00 03 5e |...W...A.......^|
00000040 00 03 00 09 43 4f 4e 54 00 00 00 40 00 00 00 00 |....CONT...@....|
00000050 00 00 00 08 28 43 29 20 32 30 30 35 00 26 00 00 |....(C) 2005.&..|
00000060 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00000080 00 00 00 00 4d 44 50 52 00 00 00 70 00 00 00 00 |....MDPR...p....|
00000090 00 02 c2 a4 00 02 c2 a4 00 00 03 e0 00 00 01 9f |................|
hexdump -C Producer11-01.rm | head
00000000 2e 52 4d 46 00 00 00 12 00 01 00 00 00 00 00 00 |.RMF............|
00000010 00 07 50 52 4f 50 00 00 00 32 00 00 00 03 6e e8 |..PROP...2....n.|
00000020 00 03 6e e8 00 00 03 e0 00 00 01 a4 00 00 01 64 |..n............d|
00000030 00 00 1b 57 00 00 05 a4 00 02 5c 35 00 00 03 5e |...W......\5...^|
00000040 00 03 00 09 43 4f 4e 54 00 00 00 40 00 00 00 00 |....CONT...@....|
00000050 00 00 00 08 28 43 29 20 32 30 30 35 00 26 00 00 |....(C) 2005.&..|
00000060 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00000080 00 00 00 00 4d 44 50 52 00 00 00 70 00 00 00 00 |....MDPR...p....|
00000090 00 02 c2 a4 00 02 c2 a4 00 00 03 e0 00 00 01 a4 |................|
They both look very similar to me. Aside from a few bytes, they are practically identical. Lets see what MediaInfo has to say.
mediainfo Producer11-01.rv
General
Complete name : Producer11-01.rv
Format : RealMedia
File size : 164 KiB
Duration : 6 s 999 ms
Overall bit rate : 225 kb/s
Frame rate : 24.000 FPS
Copyright : (C) 2005
FileExtension_Invalid : rm rmvb ra
Video
ID : 0
Format : RealVideo 4
Codec ID : RV40
Codec ID/Info : Based on AVC (H.264), Real Player 9
Duration : 6 s 999 ms
Bit rate : 181 kb/s
Width : 640 pixels
Height : 424 pixels
Display aspect ratio : 3:2
Frame rate : 24.000 FPS
Bits/(Pixel*Frame) : 0.028
Stream size : 155 KiB (94%)
Audio
ID : 1
Format : Cooker
Codec ID : cook
Codec ID/Info : Based on G.722.1, Real Player 6
Duration : 7 s 429 ms
Bit rate : 44.1 kb/s
Channel(s) : 2 channels
Sampling rate : 44.1 kHz
Bit depth : 16 bits
Stream size : 40.0 KiB (24%)
mediainfo Producer11-01.rm
General
Complete name : Producer11-01.rm
Format : RealMedia
File size : 151 KiB
Duration : 6 s 999 ms
Overall bit rate : 225 kb/s
Frame rate : 24.000 FPS
Copyright : (C) 2005
Video
ID : 0
Format : RealVideo 4
Codec ID : RV40
Codec ID/Info : Based on AVC (H.264), Real Player 9
Duration : 6 s 999 ms
Bit rate : 181 kb/s
Width : 640 pixels
Height : 424 pixels
Display aspect ratio : 3:2
Frame rate : 24.000 FPS
Bits/(Pixel*Frame) : 0.028
Stream size : 155 KiB
Audio
ID : 1
Format : Cooker
Codec ID : cook
Codec ID/Info : Based on G.722.1, Real Player 6
Bit rate : 44.1 kb/s
Channel(s) : 2 channels
Sampling rate : 44.1 kHz
Bit depth : 16 bits
Other than the RV file having a invalid file extension, they both identify as a RealMedia file and have identical properties. So it seems the RV file is really no different than the RM file. I think the best course of action for PRONOM is to deprecate these two RV PUID’s and just ad RV as an acceptable extension for the RealMedia format.
To add to the evidence, here is the output from ffprobe:
Input #0, rm, from 'Producer11-01.rm':
Metadata:
copyright : (C) 2005
comment :
ASMRuleBook : #($Bandwidth >= 0),Stream1Bandwidth = 44100, Stream0Bandwidth = 180900;
Audiences : 256k DSL or Cable;
audioMode : music
Creation Date : 11/12/2024 20:28:55
Generated By : RealProducer(R) Plus 11.1 for Windows, Build 11.1.0.2676
Modification Date: 11/12/2024 20:28:55
videoMode : normal
Duration: 00:00:07.00, start: 0.000000, bitrate: 176 kb/s
Stream #0:0: Video: rv40 (RV40 / 0x30345652), yuv420p, 640x424, 180 kb/s, 24 fps, 24 tbr, 1k tbn
Stream #0:1: Audio: cook (cook / 0x6B6F6F63), 44100 Hz, stereo, fltp, 44 kb/s
Input #0, rm, from 'Producer11-01.rv':
Metadata:
copyright : (C) 2005
comment :
ASMRuleBook : #($Bandwidth >= 0),Stream1Bandwidth = 44100, Stream0Bandwidth = 180900;
Audiences : 256k DSL or Cable;
audioMode : music
Creation Date : 11/12/2024 20:28:16
Generated By : RealProducer(R) Plus 11.1 for Windows, Build 11.1.0.2676
Modification Date: 11/12/2024 20:28:16
videoMode : normal
Duration: 00:00:07.43, start: 0.000000, bitrate: 181 kb/s
Stream #0:0: Video: rv40 (RV40 / 0x30345652), yuv420p, 640x424, 180 kb/s, 24 fps, 24 tbr, 1k tbn
Stream #0:1: Audio: cook (cook / 0x6B6F6F63), 44100 Hz, stereo, fltp, 44 kb/s
But wait, there are a couple formats we could add which are related to RealProducer. RealProducer used a few other formats to manage projects and other metadata for streaming. They include:
- .RP RealPix Image
- .RT RealText
- .RPAD RealProducer Audience File
- .RPJF RealProducer Job File
- .RPSD RealProducer Server Destination
- .RMHD RealMediaHD file
- .RAM Playlist
- .RPM Embedded RAM
Don’t get excited, the RealPix Image format really isn’t an image, it is simply an XML file with all the details of an image or group of images. Pretty boring. It was however a big thing in the day, even got a full guide written up for the process. “All information in the file occurs between an opening <imfl> tag and a closing </imfl> tag. This is the only tag that uses an end tag.” This format was the topic of discussion as malicious code could be in the RP file and executed just by having someone load your webpage. IMFL is obviously an acronym, but none of the documents I could find tells me what it stands for, so I did what everyone does now, I asked ChatGPT.
The RealPix format by RealNetworks, which was used for interactive multimedia content, indeed utilized IMFL as its tagged format. IMFL stands for “Interleaved Media File Language.” This markup was particularly designed to handle multimedia presentations, allowing the synchronization of images, audio, and video in a slideshow-style format. It used XML-like syntax where elements like <imfl>, <head>, and <fadein/> defined media objects, transitions, and their timing. Key components included attributes for positioning, color, and animation effects, making RealPix a flexible format for creating multimedia sequences compatible with RealPlayer.
For technical details, the RealPix format closely resembles SMIL (Synchronized Multimedia Integration Language) and supports strict tag closure and case sensitivity. This means all tags and attribute names must be lowercase, and attributes must be in double quotes, as seen in SMIL and RealSystem G2 markup, RealNetworks’ broader multimedia framework.
When I asked for a source, it could not give me one. So not sure if it is the correct answer, but it seems to fit. Here are some samples of RP, RT and SMIL files.
For RealText with the RT extension, we find a similar tagged text. This format is used to provide text presentations to go along with Images, Audio, or Video. The tagged text then describes when and how the text is displayed. This is all done in a player window, therefore the root tag of these RT documents starts and ends with <window>. I guess these could be considered a subtitle format for streaming media.
The SMIL files is interesting, it is known standard, but in many cases, does not have an XML declaration, therefore not identified by current PRONOM. They are used to link everything together. I might suggest a variant of the SMIL format to not have the XML declaration to identify these formats correctly.
<smil>
<body>
<par>
<textstream src=”rtsp://realserver.company.com/mary.rt”/>
<video src=”rtsp://realserver.company.com/mary.rm”/>
</par>
</body>
</smil>
The .RPAD RealProducer Audience File, .RPJF RealProducer Job File, .RPSD RealProducer Server Destination are all XML files for managing some of the configuration found in the RealProducer software.
cat 56k\ Dial-up.rpad
<?xml version="1.0" encoding="UTF-8"?>
<audience xmlns="http://ns.real.com/tools/audience.2.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://ns.real.com/tools/audience.2.0 http://ns.real.com/tools/audience.2.0.xsd">
<avgBitrate type="uint">34000</avgBitrate>
<maxBitrate type="uint">68000</maxBitrate>
<streams>
cat RealProducer11-01.rpjf
<?xml version="1.0" encoding="UTF-8"?>
<job xmlns="http://ns.real.com/tools/job.2.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://ns.real.com/tools/job.2.0 http://ns.real.com/tools/job.2.0.xsd">
<enableTwoPass type="bool">true</enableTwoPass>
<clipInfo>
cat Multicast\ Push\ Server.rpsd
<?xml version="1.0" encoding="UTF-8"?>
<destination xsi:type="pushServer" xmlns="http://ns.real.com/tools/server.2.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://ns.real.com/tools/server.2.0 http://ns.real.com/tools/server.2.0.xsd">
<pluginName type="string">rn-server-rbs</pluginName>
Those three formats should be easy enough, especially if we look for Namespace urls.
The RAM and RPM formats are simply text files with a URL. You can find some samples here and here.
An RM and RV file are the same format as the RMVB file but just with a variable bitrate. Later on a new format was used to improve the quality of video. This format has the extension RMHD, referring to RealMedia HD. Let’s take a look.
hexdump -C DSC_0009.rmhd | head
00000000 2e 52 4d 50 00 00 00 12 00 01 00 00 00 00 00 00 |.RMP............|
00000010 00 07 50 52 4f 50 00 00 00 36 00 02 00 04 f7 33 |..PROP...6.....3|
00000020 00 04 f7 33 00 00 11 bd 00 00 02 5d 00 00 01 d2 |...3.......]....|
00000030 00 00 1b 2e 00 00 00 00 00 00 00 00 00 04 65 68 |..............eh|
00000040 00 00 01 6f 00 02 00 03 43 4f 4e 54 00 00 00 12 |...o....CONT....|
00000050 00 00 00 00 00 00 00 00 00 00 4d 44 50 52 00 00 |..........MDPR..|
00000060 00 76 00 00 00 00 00 03 24 64 00 03 24 64 00 00 |.v......$d..$d..|
00000070 11 bd 00 00 04 2a 00 00 00 00 00 00 00 00 00 00 |.....*..........|
00000080 1b 2e 0c 56 69 64 65 6f 20 53 74 72 65 61 6d 14 |...Video Stream.|
00000090 76 69 64 65 6f 2f 78 2d 70 6e 2d 72 65 61 6c 76 |video/x-pn-realv|
The format looks very similar, but has the magic header of .RMP instead of .RMF. MediaInfo and FFProbe are unaware of the format. The software mentions a RV11 codec which is confusing as the codecs went from RV10-RV60.
Phew, that was a lot considering the two formats I tried to research came up the same as an existing format. There are probably others I have missed. I did see a reference to an RMX format which seems to be an encrypted RM file. The header is the same so it will identify as a RealMedia file, but with the wrong extension. Let me know if you come across any. I have some samples of the formats mentioned here, plus a proposal of new signatures on my Github repository.
