PocketSphinx – error when calling ps_unset_search

[Oren G.]

During recognition I have to switch between grammars. After using a grammar, I don’t need it anymore, so I’m trying to free the last used grammar. This is the code I use:

ps_end_utt(decoder)

name_ =  ps_get_search(decoder)
result = ps_unset_search(decoder, name_)
ps_set_jsgf_file(decoder, "2ndGrammar", "c:\sphinx\2ndGrammar.jsgf")
ps_set_search(decoder, "2ndGrammar")

ps_start_utt(decoder)

The code above does switch between the grammars, but I have two issues:

1. ps_unset_search always returns an error (-1).
2. When I finally call ps_free, the app crashes. Visual Studio gives the error:
   “A heap has been corrupted”. The error occur at the function ps_search_base_free, at the first line - ckd_free(search->name); Regarding the “name” variable, Visual Studio indicates “error reading characters of string”.

When I don’t use the ps_set_search api, I don’t have any issues with ps_free.

PS – I’m using PocketSphinx with C# binding, on Windows

[Nickolay V. Shmyrev]

I'm sorry, it is hard to understand what is going on. You write you use C# with bindings but your code in C.

I've just tried the following code and it works fine

using System;
using System.IO;
using Pocketsphinx;

public class Test
{
   public static void Main()
   {
    Config c = Decoder.DefaultConfig();
        c.SetString("-hmm", "../../model/en-us/en-us");
        c.SetString("-lm", "../../model/en-us/en-us.lm.bin");
        c.SetString("-dict", "../../model/en-us/cmudict-en-us.dict");
    Decoder d = new Decoder(c);

    byte[] data = File.ReadAllBytes("../../test/data/goforward.raw");
    d.StartUtt();
    d.ProcessRaw(data, data.Length, false, false);
    d.EndUtt();
    Console.WriteLine("Result is '{0}'", d.Hyp().Hypstr);
    foreach (Segment s in d.Seg()) {
        Console.WriteLine(s);
    }

    string name =  d.GetSearch();
    Console.WriteLine("Search is {0}", name);
        d.UnsetSearch(name);
        d.SetLmFile("another_search", "../../model/en-us/en-us.lm.bin");
        d.SetSearch("another_search");
    name =  d.GetSearch();
    Console.WriteLine("Search is {0}", name);

    data = File.ReadAllBytes("../../test/data/goforward.raw");
    d.StartUtt();
    d.ProcessRaw(data, data.Length, false, false);
    d.EndUtt();
    Console.WriteLine("Result is '{0}'", d.Hyp().Hypstr);
   }
}

Can you please provide a better example to reproduce your issue?

[Oren G.]

I have found that the error was caused by the C# binding. By this code:

[DllImport("pocketsphinx.dll", CallingConvention = CallingConvention.Cdecl)]
public static extern string ps_get_search(IntPtr decoder);

The error was fixed after changing the returned type from String to IntPtr.

[Nickolay V. Shmyrev]

I recommend you to use our official swig-created bindings.

[Oren G.]

I didn't know how to use them. There are no instructions. It took me more time to search the internet for the info on how to use them (and at the end I still don't know how) then to write my own PInvoke signatures, which work well.