Sending block blobs to Windows Media Services upload URL

Question

I'm trying to create an app which uses Windows Media Services REST API to upload video files and transcode them. Everything works great but i have encountered a situation, in which i'm not able to upload a 160 MB video file without knowing why. It's extremely painfull to debug the upload process in a regular way cause uploading 160 MB file takes ages so i decided to ask my question here:

1. I know about Azure Storage limitations of single file size (which is up to 64 MB). Is there such limitation for uploading files to Windows Media Services as well? Do i need to send that file in 4 MB chunks?

2. If so, how can actually do that using REST API ? I can send chunked file to a regular storage account but, when it comes to WMS, things are a bit different. Basically, when dealing with WMS, i need to upload my file (or file blocks) to a specific temporary url and i'm not sure how to combine that with chunks and setting a block id etc. I also can't find any info about that on the internet.

Thanks in advance for any advice!

Answer 1

You didn't say which platform are you using to build your application (I'm guessing it's .net?)

1. According to MSDN, single file (blob) is not limited to 64 MB:

   Each block can be a different size, up to a maximum of 4 MB. The maximum size for a block blob is 200 GB, and a block blob can include no more than 50,000 blocks. If you are writing a block blob that is no more than 64 MB in size, you can upload it in its entirety with a single write operation.

   This means you can upload files (blobs) which are up to 200 GB. If file is smaller than 64 MB, you can upload it as one big chunk (block). If it's bigger than 64 MB, you will have to split it into smaller blocks (up to 4 MB each) and upload it that way.

2. Full disclosure: I wrote this blog post which explains how to build an async upload page which can upload files in chunks. It uses the Azure REST API to upload all the file blocks and the Windows Azure Media Services SDK to communicate with the Media Service and create locators (temporary URL's you mentioned) which are used to upload files.

   There is quite a bit of code involved in making this work so I created a simple demo app (written in JS and .net) to go together with the post. If you're not doing this in .net, you will still be able to use the JS portion of the code, it's just that you'll need to obtain the upload locators through Azure REST API as well.
   
   

Very simplified, the upload/transcoding workflow goes something like this:

• Obtain a temporary upload URL (locator) through the back-end of your application (to secure your Azure credentials)
• Split a file into smaller chunks, upload them all to Azure storage on behalf of WAMS (Windows Azure Media Services) through the REST API while keeping track of all block ID's
• Submit an XML containing all block ID's to the REST API
• If needed, transcode videos (I used the WAMS SDK in the back-end of the app to create the encoding jobs) - each video will be a new separate Asset
• Publish assets - get locators (URL's) for accessing the original and/or transcoded videos

I also recommend you read Gaurav Mantri's post about uploading large files to Azure storage. It explains a lot and is a very good read about this topic.