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TV Tuner to WebM/H.264

Former Member

I am looking to start a project and sadly I do not even know where to begin.

 

The goal is to capture terrestrial TV signals (in the US I believe this is ATSC) via an antenna, selectively tune to a specific channel, demodulate, decompress and synchronize audio and video. Then take that A/V signal and hardware encode to WebM and/or H.264. Ultimately, take that video and provide it as a data stream that can be sent over HTTP. I want to eventually make it a nice little self-contained package that I can just plug an antenna into on one end and an ethernet port into the other. Navigate to the website on the device and see video.

 

The good news is that I have already prototyped the entire process in software: Fedora 19, HVR-2250, FFmpeg, FFServer, Apache2. I concede that the HVR-2250 is hardware, but from the level I am using it, its essentially software to me; I digress.

 

I have been looking for packages and reference designs for demodulation and decompressions of ATSC signals but cannot seem to find the right keywords to search. Alternatively, it could be that I am getting valid results and am to dense to understand how the results apply to what I am trying to achieve.

 

Ultimately, I am not looking for someone to design the whole thing for me. I am just looking to figure out where to start (e.g., reference designs, part numbers, etc...). After all, I have a degree in EE so I am familar with Ohm's law and such. image

  • Hello Ryan,

     

    Maybe I'm stating the obvious, but can't VLC do this with a tuner card? I'm in Europe, and use a cheap DVB-T (Digital Video Broadcast - Terrestrial) receiver to occasionally view television on my computer. I know VLC can also convert/stream, so this would seem the "easy" approach, of course with very little EE challenge.

  • in reply to vsluiter

    You are absolutely right. And in fact I have already done that, that is why I called out Fedora 19, HVR-2250, FFmpeg (libavcodec/libavformat is a shared library between VLC and FFmpeg), FFserver, and Apache2. I have a completely working software stack that achieves exactly what I am looking to do.

     

    The problem with that architecture is it does not scale. That is, I cannot easily add more encoding through-put. For example, if it takes my 4 Xeon CPUs to encode 1 stream at 720p@30fps for both WebM and H.264. Then to encode 2 streams I need a whole new computer! The HVR-2250 has 2 tuners and thus I should be able to use both. What do I do if I buy a tuner card with 4 tuners? Buy 4 new computers? What do I do if I want 1080p@30fps? Never mind the fact that the computer is also my NAS and I do not want all of its cycles over run encoding TV streams.

     

    Honestly, I do understand that newer desktop hardware would probably allow this to work and not require 4 computers. I am, of course, being hyperbolic.

     

    But in my opinion if I am going to buy a new computer purpose built to perform this task, why not build my own hardware to achieve the same goal? In my estimation, this is how one expands their horizons.

  • in reply to Former Member

    Ryan Lovelett wrote:

    why not build my own hardware to achieve the same goal?

    I was not sure which bit of the existing hardware are you planning to re-use, and which bit do you plan to implement.

    It looks like the HVR card contains the tuner and the ADC and the MPEG hardware all built-in.

    One good way to get a reference design may be to see which vendor parts are on the board, and check to see if they offer a reference design. However, you may find custom programmable logic or custom software on the board. The code (for the programmable logic or for any processor) may have some modules from a third party, licensed.

    If the TV industry is anything like some other industries then the standards which define the expected behavior may run to tens or hundreds of thousands of pages in what can seem as many documents. They may or may not be free to download from the standards body - unfortunately I'm not familiar with these standards, but hopefully these pointers may help you. Also, the standards may supply some reference files of data, but they may not indicate the actual code (just pseudo-code), so there may be quite a bit of implementation to do.

    In theory, it should be possible to plug in multiple items of hardware into a PC and bring up multiple instances of your existing software, one instance for each tuner, but I don't know if the HVR hardware and software supports that.

  • in reply to Former Member

    FREESCALE SEMICONDUCTOR - MCIMX6Q-SL - I.MX6, HDMI, LVDS, RJ45, SABRE LITE BOARD

      • Core Architecture:ARM
      • Core Sub-Architecture:Cortex-A9
      • Silicon Core Number:i.MX6
      • Silicon Family Name:i.MX6 Quad

      "Multi-stream-capable HD video engine delivering H.264 1080p60 decode, 1080p30 encode,

      and 3-D video playback in HD"

       

    http://www.farnell.com/datasheets/1672220.pdf

     

    Newark Part Number: 05W6138

    http://www.newark.com/freescale-semiconductor/mcimx6q-sl/i-mx6-hdmi-lvds-rj45-sabre-lite/dp/05W6138?in_merch=Popular%20Products&in_merch=Popular%20Products&MER=PPSO_N_C_EverywhereElse_None

  • I have found a couple of tuner chips:

     

     

    I couple of things are not clear to me initially. Why the range of cost? A range of $15-$3 per chip seems like a heck of a range. What would I look at to try and evaluate one chip against another?

     

    The other is I am not exactly sure the "output" of the chips are. The best I can gather is the chips output a "baseband" signal. Is it fair to say that this output is just the output of a bandpass filter "tuned" to a specific channel frequency (e.g., channel 32 => 579.25 MHz)? If not can someone explain or point me to reading about what I should be expecting as output from these chips?