Convert video with vp9 codec using ffmpeg

Question

While I know there are cleaner more efficient programs out there for BFS traversal in other languages, in c it gets a bit lengthy
I've found some really lengthy and complicated programs on leetcode, as a beginner those are a little hard to understand, while I understand the basic concept behind it I found a much simpler and cleaner code here sanfoundry but it doesn't work for some reason? I'd be grateful if someone can help me out with this :)

#include <stdio.h>
#include <stdlib.h>
 
struct btnode
{ 
    int value; 
    struct btnode *left, *right; 
}; 
typedef struct btnode node;
 
/* function declarations */
void insert(node *, node *);
void bfs_traverse(node *);
 
/*global declarations */
node *root = NULL;
int val, front = 0, rear = -1, i;
int queue[20];
 
void main() 
{ 
    node *new = NULL ; 
    int num = 1; 
    printf("Enter the elements of the tree(enter 0 to exit)\n"); 
    while (1) 
    {     
        scanf("%d",  &num); 
        if (num  ==  0) 
            break; 
        new = malloc(sizeof(node)); 
        new->left = new->right = NULL; 
        new->value = num; 
        if (root == NULL) 
            root = new; 
        else 
        { 
            insert(new, root); 
        } 
    }
    printf("elements in a tree in inorder are\n"); 
    queue[++rear] = root->value;
    bfs_traverse(root);
    for (i = 0;i <= rear;i++)
        printf("%d -> ", queue[i]);
    printf("%d\n", root->right->right->right->value);
}
 
/* inserting nodes of a tree */
void insert(node * new , node *root) 
{ 
    if (new->value>root->value) 
    {     
        if (root->right == NULL) 
            root->right = new; 
        else 
            insert (new, root->right); 
    } 
    if (new->value < root->value) 
    {     
        if (root->left  ==  NULL) 
            root->left = new; 
        else 
            insert (new, root->left); 
    }     
}
 
/* displaying elements using BFS traversal */
void bfs_traverse(node *root)
{
    val = root->value;
    if ((front <= rear)&&(root->value == queue[front]))
    {
        if (root->left != NULL)
            queue[++rear] = root->left->value;
        if (root->right != NULL || root->right  ==  NULL)
            queue[++rear] = root->right->value;
        front++;
    }
    if (root->left != NULL)
    {
        bfs_traverse(root->left);
    }
    if (root->right != NULL)
    {
        bfs_traverse(root->right);
    }
}

Solution 1

The most basic command is:

ffmpeg -i input.mp4 -c:v libvpx-vp9 -c:a libopus output.webm

See FFmpeg Wiki: VP9 for more info.

Solution 2

With my version of ffmpeg,

$ ffmpeg -version
ffmpeg version 2.3.3 Copyright (c) 2000-2014 the FFmpeg developers

the command looks like this

ffmpeg -y -i input.mkv -c:v libvpx-vp9 -b:v 2000k -pass 1 -an -f webm /dev/null
ffmpeg    -i input.mkv -c:v libvpx-vp9 -b:v 2000k -pass 2 -c:a opus -b:a 64k -f webm output.webm

i.e.

• leave out the experimental flags
• do a two pass encoding, because the first two seconds of the output are blurry otherwise. Doing a two pass encoding is also faster than single pass.
• when doing 2 pass, you do not need to encode the audio in the first pass as @FrankGalligan noted in a comment

Single pass is/was broken, according to http://wiki.webmproject.org/vp9/known-issues

Comments

[Joel Purra]

brew install ffmpeg --with-libvpx --with-opus

[Aaron Franke]

@JoelPurra Usage: brew install [options] formula|cask [...] Error: invalid option: --with-libvpx

[trincot]

Why is there no feedback on the answer that was given?

[Pavel Binar]

I installed ffmpeg and all its components via this guide and it works now! sites.google.com/a/webmproject.org/wiki/ffmpeg/…

[FrankGalligan]

Do not set -strict experimental. That was for older FFmpeg. When doing 2 pass, you do not need to encode the audio in the first pass. ffmpeg -y -i input.mkv -c:v libvpx-vp9 -b:v 2000k -pass 1 -an -f webm /dev/null ffmpeg -i input.mkv -c:v libvpx-vp9 -b:v 2000k -pass 2 -c:a opus -b:a 64k -f webm output.webm

[Aaron Franke]

How do I check if the input file has VP9 or some other codec?

[Admin]

Its odd no one uses cq. What is your reason to use webm vs mkv?