A device configured to decode a bitstream representative of a higher order ambisonic, HOA, audio signal that is provided in multiple layers and comprises at least one HOA coefficient corresponding to a spherical harmonic basis function having an order greater than one, the device comprising: a memory configured to store the bitstream; and one or more processors configured to: - obtain, from the bitstream, an indication of a total number of transport channels (59A-D, 61A-B) specified in the bitstream; - determine whether the bitstream is provided in multiple layers; - in response to determining that the bitstream is provided in multiple layers, obtain, from the bitstream, an indication of the number of layers (21A-C) specified in the bitstream; and - obtain the layers of the bitstream based on the indication of the number of layers specified in the bitstream, the indication of the number of transport channels specified in the bitstream, and a number of channels representative of a minimum HOA order of a background soundfield of the audio signal, wherein obtaining the number of layers specified in the bitstream comprises obtaining an indication of a number of transport channels for each layer based on a syntax element included in the bitstream for the layer, wherein the indications of numbers of transport channels for the layers are obtained iteratively while a number of remaining transport channels is greater than one, the number of remaining transport channels calculated at each iteration to be the total number of transport channels minus the cumulative sum of the already-obtained numbers of transport channels, wherein, at each iteration, the indication of the number of transport channels for the respective layer is coded in the bitstream using a number of bits calculated based on the number of remaining transport channels, wherein the indication of the number of layers specified in the bitstream is obtained by incrementing a counter at each iteration, wherein if, following the iterations, the number of remaining channels is equal to one, then the number of layers is incremented by one and the number of transport channels for a final layer is set equal to one. a memory configured to store the bitstream; and one or more processors configured to: - obtain, from the bitstream, an indication of a total number of transport channels (59A-D, 61A-B) specified in the bitstream; - determine whether the bitstream is provided in multiple layers; - in response to determining that the bitstream is provided in multiple layers, obtain, from the bitstream, an indication of the number of layers (21A-C) specified in the bitstream; and - obtain the layers of the bitstream based on the indication of the number of layers specified in the bitstream, the indication of the number of transport channels specified in the bitstream, and a number of channels representative of a minimum HOA order of a background soundfield of the audio signal, - obtain, from the bitstream, an indication of a total number of transport channels (59A-D, 61A-B) specified in the bitstream; - determine whether the bitstream is provided in multiple layers; - in response to determining that the bitstream is provided in multiple layers, obtain, from the bitstream, an indication of the number of layers (21A-C) specified in the bitstream; and - obtain the layers of the bitstream based on the indication of the number of layers specified in the bitstream, the indication of the number of transport channels specified in the bitstream, and a number of channels representative of a minimum HOA order of a background soundfield of the audio signal, wherein obtaining the number of layers specified in the bitstream comprises obtaining an indication of a number of transport channels for each layer based on a syntax element included in the bitstream for the layer, wherein the indications of numbers of transport channels for the layers are obtained iteratively while a number of remaining transport channels is greater than one, the number of remaining transport channels calculated at each iteration to be the total number of transport channels minus the cumulative sum of the already-obtained numbers of transport channels, wherein, at each iteration, the indication of the number of transport channels for the respective layer is coded in the bitstream using a number of bits calculated based on the number of remaining transport channels, wherein the indication of the number of layers specified in the bitstream is obtained by incrementing a counter at each iteration, wherein if, following the iterations, the number of remaining channels is equal to one, then the number of layers is incremented by one and the number of transport channels for a final layer is set equal to one.